Use the new path to the linter package (flutter#7230)

Author: YoungSeok Yoon

packages/flutter_tools/BUILD.gn

@@ -11,6 +11,7 @@ dart_package("flutter_tools") {
 
   deps = [
     "//dart/pkg/analyzer",
+    "//dart/third_party/pkg/linter",
     "//third_party/dart-pkg/pub/archive",
     "//third_party/dart-pkg/pub/args",
     "//third_party/dart-pkg/pub/coverage",
@@ -20,7 +21,6 @@ dart_package("flutter_tools") {
     # because it uses mirrors which Fuchsia's Dart VM doesn't support.
     "//third_party/dart-pkg/pub/json_rpc_2",
     "//third_party/dart-pkg/pub/json_schema",
-    "//third_party/dart-pkg/pub/linter",
     "//third_party/dart-pkg/pub/meta",
     "//third_party/dart-pkg/pub/mustache",
     "//third_party/dart-pkg/pub/package_config",