Version 2.9.0-21.4.beta

* Cherry-pick 66cb8a8ed841a3a245f07aa878de311e8c60988f to beta
* Cherry-pick 897706edbdbdd1e08601387b95dc931edde55e75 to beta
diff --git a/DEPS b/DEPS
index de99bfd..4110d3e 100644
--- a/DEPS
+++ b/DEPS
@@ -127,7 +127,7 @@
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_rev": "86fbb2cde9bbc66c8d159909d2f65a5981ea5b50",
   "protobuf_rev": "3746c8fd3f2b0147623a8e3db89c3ff4330de760",
-  "pub_rev": "6178cdf284baf2345d1ea578b7176a754aa576fe",
+  "pub_rev": "85bdb898aeb2ac7cea76489ba0bf4e52ff7a79bf",
   "pub_semver_tag": "v1.4.4",
   "quiver-dart_tag": "246e754fe45cecb6aa5f3f13b4ed61037ff0d784",
   "resource_rev": "f8e37558a1c4f54550aa463b88a6a831e3e33cd6",
diff --git a/pkg/nnbd_migration/lib/migration_cli.dart b/pkg/nnbd_migration/lib/migration_cli.dart
index 8573990..6ad3aa9 100644
--- a/pkg/nnbd_migration/lib/migration_cli.dart
+++ b/pkg/nnbd_migration/lib/migration_cli.dart
@@ -168,9 +168,6 @@
       _logger.stderr('');
       _logger.stderr('Visit https://dart.dev/tools/pub/cmd/pub-outdated for '
           'more information.');
-      _logger.stderr('');
-      _logger.stderr('You can force migration with '
-          "'--${CommandLineOptions.skipPubOutdatedFlag}' (not recommended).");
       return false;
     }
     return true;
diff --git a/tools/VERSION b/tools/VERSION
index 4cf53fd..c041bdd 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -34,6 +34,6 @@
 MINOR 9
 PATCH 0
 PRERELEASE 21
-PRERELEASE_PATCH 2
+PRERELEASE_PATCH 4
 ABI_VERSION 38
 OLDEST_SUPPORTED_ABI_VERSION 38