update deprecated package references (#1032)

diff --git a/lib/src/rules/no_duplicate_case_values.dart b/lib/src/rules/no_duplicate_case_values.dart
index d0398ac..0808ef3 100644
--- a/lib/src/rules/no_duplicate_case_values.dart
+++ b/lib/src/rules/no_duplicate_case_values.dart
@@ -5,7 +5,7 @@
 import 'dart:collection';
 
 import 'package:analyzer/analyzer.dart';
-import 'package:analyzer/context/declared_variables.dart';
+import 'package:analyzer/dart/analysis/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_resolution_map.dart';
 import 'package:analyzer/error/listener.dart';
diff --git a/lib/src/rules/prefer_contains.dart b/lib/src/rules/prefer_contains.dart
index 30a45f8..dab6654 100644
--- a/lib/src/rules/prefer_contains.dart
+++ b/lib/src/rules/prefer_contains.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/analyzer.dart';
-import 'package:analyzer/context/declared_variables.dart';
+import 'package:analyzer/dart/analysis/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
diff --git a/lib/src/rules/prefer_is_empty.dart b/lib/src/rules/prefer_is_empty.dart
index 49f14c0..99c8c96 100644
--- a/lib/src/rules/prefer_is_empty.dart
+++ b/lib/src/rules/prefer_is_empty.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/analyzer.dart';
-import 'package:analyzer/context/declared_variables.dart';
+import 'package:analyzer/dart/analysis/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';