gopls: fix non-constant format strings

Fix vet failures related to the new vet check for non-constant format
strings with no args (golang/go#60529).

Change-Id: If63006613ec4827b8f7d23990654f5ecc1521ec8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/610795
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

gopls/internal/cache/view.go

@@ -706,7 +706,7 @@ func (s *Snapshot) initialize(ctx context.Context, firstAttempt bool) {
 		}
 	case len(modDiagnostics) > 0:
 		initialErr = &InitializationError{
-			MainError: fmt.Errorf(modDiagnostics[0].Message),
+			MainError: errors.New(modDiagnostics[0].Message),
 		}
 	}
 

gopls/internal/golang/completion/statements.go

@@ -408,7 +408,7 @@ func (c *completer) addReturnZeroValues() {
 		snip.WritePlaceholder(func(b *snippet.Builder) {
 			b.WriteText(zero)
 		})
-		fmt.Fprintf(&label, zero)
+		fmt.Fprint(&label, zero)
 	}
 
 	c.items = append(c.items, CompletionItem{

gopls/internal/test/integration/fake/editor.go

@@ -663,7 +663,7 @@ func (e *Editor) SaveBufferWithoutActions(ctx context.Context, path string) erro
 	defer e.mu.Unlock()
 	buf, ok := e.buffers[path]
 	if !ok {
-		return fmt.Errorf(fmt.Sprintf("unknown buffer: %q", path))
+		return fmt.Errorf("unknown buffer: %q", path)
 	}
 	content := buf.text()
 	includeText := false