Run gopls modernize on codebase (#34751)

Recent modernize fixes:
https://github.com/golang/tools/commits/master/gopls/internal/analysis/modernize

modules/markup/markdown/transform_heading.go

@@ -16,7 +16,7 @@ import (
 func (g *ASTTransformer) transformHeading(_ *markup.RenderContext, v *ast.Heading, reader text.Reader, tocList *[]Header) {
 	for _, attr := range v.Attributes() {
 		if _, ok := attr.Value.([]byte); !ok {
-			v.SetAttribute(attr.Name, []byte(fmt.Sprintf("%v", attr.Value)))
+			v.SetAttribute(attr.Name, fmt.Appendf(nil, "%v", attr.Value))
 		}
 	}
 	txt := v.Text(reader.Source()) //nolint:staticcheck