clean up some no-op toString()s (#3588)

Author: pq

tool/canonical/scorecard.dart

@@ -187,7 +187,7 @@ class LintScore {
   bool get inFlutter => ruleSets.contains('flutter');
   bool get inRecommended => ruleSets.contains('recommended');
 
-  String get _ruleSets => ruleSets.isNotEmpty ? ' ${ruleSets.toString()}' : '';
+  String get _ruleSets => ruleSets.isNotEmpty ? ' $ruleSets' : '';
 
   String toMarkdown(List<Detail> details) {
     var sb = StringBuffer('| ');
@@ -311,7 +311,7 @@ class ScoreCard {
       for (var bug in bugs) {
         var title = bug.title;
         if (title.contains(lint.name)) {
-          bugReferences.add('#${bug.number.toString()}');
+          bugReferences.add('#${bug.number}');
         }
       }
 

tool/doc.dart

@@ -495,7 +495,7 @@ class MarkdownIndexer {
     }
 
     if (filePath == null) {
-      print(buffer.toString());
+      print(buffer);
     } else {
       File('$filePath/index.md').writeAsStringSync(buffer.toString());
     }
@@ -775,7 +775,7 @@ class RuleMarkdownGenerator {
     }
 
     if (filePath == null) {
-      print(buffer.toString());
+      print(buffer);
     } else {
       File('$filePath/$name.md').writeAsStringSync(buffer.toString());
     }

tool/scorecard.dart

@@ -157,7 +157,7 @@ class LintScore {
       this.bugReferences,
       this.since});
 
-  String get _ruleSets => ruleSets!.isNotEmpty ? ' ${ruleSets.toString()}' : '';
+  String get _ruleSets => ruleSets!.isNotEmpty ? ' $ruleSets' : '';
 
   String toMarkdown(List<Detail> details) {
     var sb = StringBuffer('| ');
@@ -265,7 +265,7 @@ class ScoreCard {
       for (var bug in bugs) {
         var title = bug.title;
         if (title.contains(lint.name)) {
-          bugReferences.add('#${bug.number.toString()}');
+          bugReferences.add('#${bug.number}');
         }
       }