Update tooling to use new `rules.json` location (dart-lang/lints#140)

* Update tooling to use new 'rules.json' location

* Use dart.dev version of generated file
diff --git a/pkgs/lints/tool/gen_docs.dart b/pkgs/lints/tool/gen_docs.dart
index 43f494f..3a5caca 100644
--- a/pkgs/lints/tool/gen_docs.dart
+++ b/pkgs/lints/tool/gen_docs.dart
@@ -16,7 +16,7 @@
 
   final rulesJsonFile = File('tool/rules.json');
   final rulesUrl =
-      'https://dart-lang.github.io/linter/lints/machine/rules.json';
+      'https://raw.githubusercontent.com/dart-lang/site-www/main/src/_data/linter_rules.json';
   if (!justVerify) {
     rulesJsonFile.writeAsStringSync((await http.get(Uri.parse(rulesUrl))).body);
   }
@@ -54,7 +54,7 @@
       print('${readmeFile.path} is not up-to-date (lint tables need to be '
           'regenerated).');
       print('');
-      print("Run 'dart tools/gen_docs.dart' to re-generate.");
+      print("Run 'dart tool/gen_docs.dart' to re-generate.");
       exit(1);
     } else {
       print('${readmeFile.path} is up-to-date.');
@@ -93,7 +93,7 @@
       if (ruleMeta == null) {
         print('rules.json data for rule \'$rule\' not found.');
         print('Update lib/rules.json from '
-            'https://dart-lang.github.io/linter/lints/machine/rules.json.');
+            'https://raw.githubusercontent.com/dart-lang/site-www/main/src/_data/linter_rules.json.');
         exit(1);
       }
       final description = ruleMeta['description'] as String?;