Remove references to pkg:plugin in DEPS and .packages

Fixes dart-lang#36221

Change-Id: Ic804d223c4dbbb82bb9f8d448fc209d37c79da39
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/97044
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Kevin Moore <[email protected]>

Author: kevmoo

.packages

@@ -65,7 +65,6 @@ observatory:runtime/observatory/lib
 package_config:third_party/pkg_tested/package_config/lib
 package_resolver:third_party/pkg_tested/package_resolver/lib
 path:third_party/pkg/path/lib
-plugin:third_party/pkg/plugin/lib
 pool:third_party/pkg/pool/lib
 protobuf:third_party/pkg/protobuf/protobuf/lib
 pub:third_party/pkg/pub/lib

DEPS

@@ -108,7 +108,6 @@ vars = {
   "package_config_tag": "1.0.5",
   "package_resolver_tag": "1.0.10",
   "path_tag": "1.6.2",
-  "plugin_tag": "f5b4b0e32d1406d62daccea030ba6457d14b1c47",
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_tag": "1.3.6",
   "protobuf_rev": "0c77167b16d00b561a6055bfe26690af7f26ae88",
@@ -303,8 +302,6 @@ deps = {
       + "@" + Var("package_resolver_tag"),
   Var("dart_root") + "/third_party/pkg/path":
       Var("dart_git") + "path.git" + "@" + Var("path_tag"),
-  Var("dart_root") + "/third_party/pkg/plugin":
-      Var("dart_git") + "plugin.git" + "@" + Var("plugin_tag"),
   Var("dart_root") + "/third_party/pkg/pool":
       Var("dart_git") + "pool.git" + "@" + Var("pool_tag"),
   Var("dart_root") + "/third_party/pkg/protobuf":