Fix hints in the analysis_server package.

pkg/analysis_server/lib/src/context_manager.dart

Index: pkg/analysis_server/lib/src/context_manager.dart
diff --git a/pkg/analysis_server/lib/src/context_manager.dart b/pkg/analysis_server/lib/src/context_manager.dart
index f0159981fd1b44bea863f470c8117ea621d1a777..058662c887d0fcc273258bb9fdde87cc565aa162 100644
--- a/pkg/analysis_server/lib/src/context_manager.dart
+++ b/pkg/analysis_server/lib/src/context_manager.dart
@@ -285,7 +285,7 @@ abstract class ContextManager {
     List<Resource> children;
     try {
       children = folder.getChildren();
-    } on FileSystemException catch (exception) {
+    } on FileSystemException {
       // The folder no longer exists, or cannot be read, to there's nothing to
       // do.
       return;