switch from unused_imports to deprecated to test unfixable warnings

The unused_imports warning is going to emit fixable suggestions in the
near future, but that means parts of the cargo's test suite will break.
This commit switches the tests to use the deprecated warning, which
*shouldn't* be fixable at all.

tests/testsuite/fix.rs

@@ -702,11 +702,11 @@ fn fix_features() {
 #[test]
 fn shows_warnings() {
     let p = project()
-        .file("src/lib.rs", "use std::default::Default; pub fn foo() {}")
+        .file("src/lib.rs", "#[deprecated] fn bar() {} pub fn foo() { let _ = bar(); }")
         .build();
 
     p.cargo("fix --allow-no-vcs")
-        .with_stderr_contains("[..]warning: unused import[..]")
+        .with_stderr_contains("[..]warning: use of deprecated item[..]")
         .run();
 }
 
@@ -984,20 +984,22 @@ fn shows_warnings_on_second_run_without_changes() {
         .file(
             "src/lib.rs",
             r#"
-                use std::default::Default;
+                #[deprecated]
+                fn bar() {}
 
                 pub fn foo() {
+                    let _ = bar();
                 }
             "#,
         )
         .build();
 
     p.cargo("fix --allow-no-vcs")
-        .with_stderr_contains("[..]warning: unused import[..]")
+        .with_stderr_contains("[..]warning: use of deprecated item[..]")
         .run();
 
     p.cargo("fix --allow-no-vcs")
-        .with_stderr_contains("[..]warning: unused import[..]")
+        .with_stderr_contains("[..]warning: use of deprecated item[..]")
         .run();
 }
 
@@ -1007,65 +1009,76 @@ fn shows_warnings_on_second_run_without_changes_on_multiple_targets() {
         .file(
             "src/lib.rs",
             r#"
-                use std::default::Default;
+                #[deprecated]
+                fn bar() {}
 
-                pub fn a() -> u32 { 3 }
+                pub fn foo() {
+                    let _ = bar();
+                }
             "#,
         )
         .file(
             "src/main.rs",
             r#"
-                use std::default::Default;
-                fn main() { println!("3"); }
+                #[deprecated]
+                fn bar() {}
+
+                fn main() {
+                    let _ = bar();
+                }
             "#,
         )
         .file(
             "tests/foo.rs",
             r#"
-                use std::default::Default;
+                #[deprecated]
+                fn bar() {}
+
                 #[test]
                 fn foo_test() {
-                    println!("3");
+                    let _ = bar();
                 }
             "#,
         )
         .file(
             "tests/bar.rs",
             r#"
-                use std::default::Default;
+                #[deprecated]
+                fn bar() {}
 
                 #[test]
                 fn foo_test() {
-                    println!("3");
+                    let _ = bar();
                 }
             "#,
         )
         .file(
             "examples/fooxample.rs",
             r#"
-                use std::default::Default;
+                #[deprecated]
+                fn bar() {}
 
                 fn main() {
-                    println!("3");
+                    let _ = bar();
                 }
             "#,
         )
         .build();
 
     p.cargo("fix --allow-no-vcs --all-targets")
-        .with_stderr_contains(" --> examples/fooxample.rs:2:21")
-        .with_stderr_contains(" --> src/lib.rs:2:21")
-        .with_stderr_contains(" --> src/main.rs:2:21")
-        .with_stderr_contains(" --> tests/bar.rs:2:21")
-        .with_stderr_contains(" --> tests/foo.rs:2:21")
+        .with_stderr_contains(" --> examples/fooxample.rs:6:29")
+        .with_stderr_contains(" --> src/lib.rs:6:29")
+        .with_stderr_contains(" --> src/main.rs:6:29")
+        .with_stderr_contains(" --> tests/bar.rs:7:29")
+        .with_stderr_contains(" --> tests/foo.rs:7:29")
         .run();
 
     p.cargo("fix --allow-no-vcs --all-targets")
-        .with_stderr_contains(" --> examples/fooxample.rs:2:21")
-        .with_stderr_contains(" --> src/lib.rs:2:21")
-        .with_stderr_contains(" --> src/main.rs:2:21")
-        .with_stderr_contains(" --> tests/bar.rs:2:21")
-        .with_stderr_contains(" --> tests/foo.rs:2:21")
+        .with_stderr_contains(" --> examples/fooxample.rs:6:29")
+        .with_stderr_contains(" --> src/lib.rs:6:29")
+        .with_stderr_contains(" --> src/main.rs:6:29")
+        .with_stderr_contains(" --> tests/bar.rs:7:29")
+        .with_stderr_contains(" --> tests/foo.rs:7:29")
         .run();
 }