Rollup merge of #100351 - compiler-errors:diagnostic-convention, r=fee1-dead

Use `&mut Diagnostic` instead of `&mut DiagnosticBuilder` unless needed

This seems to be the established convention (02ff9e0) when `DiagnosticBuilder` was first added. I am guilty of introducing some of these.

compiler/rustc_parse/src/parser/expr.rs

@@ -859,7 +859,7 @@ impl<'a> Parser<'a> {
             );
             let mut err = self.struct_span_err(span, &msg);
 
-            let suggest_parens = |err: &mut DiagnosticBuilder<'_, _>| {
+            let suggest_parens = |err: &mut Diagnostic| {
                 let suggestions = vec![
                     (span.shrink_to_lo(), "(".to_string()),
                     (span.shrink_to_hi(), ")".to_string()),