Bump dartdoc to 0.32.3 and tighten doc quality checker (#63111)

dev/tools/dartdoc_checker.dart

diff --git a/dev/tools/dartdoc_checker.dart b/dev/tools/dartdoc_checker.dart
index 9340b40..686e918 100644
--- a/dev/tools/dartdoc_checker.dart
+++ b/dev/tools/dartdoc_checker.dart
@@ -85,14 +85,9 @@
 
 int _scanFile(File file) {
   assert(path.extension(file.path) == 'html');
-  Iterable<String> matches = _pattern.allMatches(file.readAsStringSync())
+  final Iterable<String> matches = _pattern.allMatches(file.readAsStringSync())
       .map((RegExpMatch m ) => m.group(0));
 
-  // TODO(goderbauer): Remove this exception when https://github.com/dart-lang/dartdoc/issues/1945 is fixed.
-  matches = matches
-      .where((String m) => m != '{@inject-html}')
-      .where((String m) => m != '{@end-inject-html}');
-
   if (matches.isNotEmpty) {
     stderr.writeln('Found unresolved dartdoc directives in ${file.path}:');
     for (final String match in matches) {