Bump pub to 8c2e621c2403cb503cc9959be387d1061a16846a

Changes:
```
> git log --format="%C(auto) %h %s" 1d7b0d9..8c2e621
 https://dart.googlesource.com/pub.git/+/8c2e621c Special case global-run message for updated sdk (4419)
 https://dart.googlesource.com/pub.git/+/afdd62c5 Bump actions/checkout from 4.2.0 to 4.2.2 in the github-actions group (4420)
 https://dart.googlesource.com/pub.git/+/e0df88b0 blast_repo fixes (remove lint package_api_docs) (4416)
 https://dart.googlesource.com/pub.git/+/489d15c1 Remove stray files (4413)
 https://dart.googlesource.com/pub.git/+/776def48 Clean up duplicate lints (4407)

```

Diff: https://dart.googlesource.com/pub.git/+/1d7b0d9a35be9cff5d071f6cf17fcdcde2b7ecc5..8c2e621c2403cb503cc9959be387d1061a16846a/
Change-Id: Id782c431b64a95f1f9bc39492a66e32bc270afe6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/393742
Reviewed-by: Jonas Jensen <jonasfj@google.com>
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>

DEPS

@@ -156,7 +156,7 @@ vars = {
   "package_config_rev": "2583a4e2f9382409ba3bcfa4887ef2a2a8a2aee3",
   "pool_rev": "0bac9b20ef61ad8bfdd6b92b565dd12e8e2e2c78",
   "protobuf_rev": "ccf104dbc36929c0f8708285d5f3a8fae206343e",
-  "pub_rev": "1d7b0d9a35be9cff5d071f6cf17fcdcde2b7ecc5", # disable tools/rev_sdk_deps.dart
+  "pub_rev": "8c2e621c2403cb503cc9959be387d1061a16846a", # disable tools/rev_sdk_deps.dart
   "pub_semver_rev": "ab3eab50cc9f3df650ba7f5571aa2a1ea715dcc8",
   "shelf_rev": "1a141c71e201ed361aabc1d89a21181667f0b39c",
   "source_maps_rev": "b20b97003a48d78a1ecba7e46d932ea4b480dd94",