Add regression test for 98444

tests/ui/lint/unconditional_panic_98444.rs

@@ -0,0 +1,7 @@
+// build-fail
+
+fn main() {
+    let xs: [i32; 5] = [1, 2, 3, 4, 5];
+    let _ = &xs;
+    let _ = xs[7]; //~ ERROR: this operation will panic at runtime [unconditional_panic]
+}

tests/ui/lint/unconditional_panic_98444.stderr

@@ -0,0 +1,10 @@
+error: this operation will panic at runtime
+  --> $DIR/unconditional_panic_98444.rs:6:13
+   |
+LL |     let _ = xs[7];
+   |             ^^^^^ index out of bounds: the length is 5 but the index is 7
+   |
+   = note: `#[deny(unconditional_panic)]` on by default
+
+error: aborting due to previous error
+