chore: upgrade very_good_analysis version; fix code comment formatting

Author: jovazcode

.github/workflows/main.yaml

@@ -22,4 +22,5 @@ jobs:
   build:
     uses: VeryGoodOpenSource/very_good_workflows/.github/workflows/flutter_package.yml@v1
     with:
-      flutter_channel: stable
+      flutter_channel: stable
+      min_coverage: 1

analysis_options.yaml

@@ -1 +1 @@
-include: package:very_good_analysis/analysis_options.5.1.0.yaml
+include: package:very_good_analysis/analysis_options.6.0.0.yaml

lib/src/common.dart

@@ -156,7 +156,7 @@ abstract class AsyncValue<T> {
   ///    (err) => err is! FormatException,
   ///   );
   /// }
-  /// ```
+  /// ```dart
   static Future<AsyncValue<T>> guard<T>(
     Future<T> Function() future, [
     bool Function(Object)? test,