Bump pub to be6868ba132c782d9835b1638a634ecb73428579

Changes:
```
> git log --format="%C(auto) %h %s" 42819a1..be6868b
 https://dart.googlesource.com/pub.git/+/be6868ba Improve precompilation (4005)
 https://dart.googlesource.com/pub.git/+/1ff7ed9f `upgrade --tighten` (3957)
 https://dart.googlesource.com/pub.git/+/a2ff15af Bump actions/checkout from 3.5.3 to 3.6.0 (4007)
 https://dart.googlesource.com/pub.git/+/9c041f97 Revert "Validate pubspec names after resolution, instead of when parsing (3956)" (4006)
 https://dart.googlesource.com/pub.git/+/62981e8c Switch vendor to a dev dependency (3997)
 https://dart.googlesource.com/pub.git/+/edcd5c2a Don't display detailed errors from credentials file (4004)
 https://dart.googlesource.com/pub.git/+/bddb0b8a Fix test expectation (4000)
 https://dart.googlesource.com/pub.git/+/c5541b33 Fix spelling errors (3999)
 https://dart.googlesource.com/pub.git/+/ee3f0ff7 Log missing compilation output (3992)
 https://dart.googlesource.com/pub.git/+/57e5d581 Remove remaining remnants of old packages folder and .packages file (3989)
 https://dart.googlesource.com/pub.git/+/edc76a1c Cleanup meta annotation usage (3990)
 https://dart.googlesource.com/pub.git/+/d619b373 Replace Pair usage with records (3988)
 https://dart.googlesource.com/pub.git/+/923cb7bd Enable lints to use new language features (3987)
 https://dart.googlesource.com/pub.git/+/78a39b05 Fix some type related lints (3986)
 https://dart.googlesource.com/pub.git/+/f41c6c80 Update Dart spec reserved words (3984)
 https://dart.googlesource.com/pub.git/+/6c267643 Fix and increase flexibility of language version override test (3985)
 https://dart.googlesource.com/pub.git/+/037138e6 Validate pubspec names after resolution, instead of when parsing (3956)
 https://dart.googlesource.com/pub.git/+/4d4ff446 Show dependency type changes in report (3954)
 https://dart.googlesource.com/pub.git/+/996fdcfd `pub add` Rely on git sources validation of --git-url (3951)
 https://dart.googlesource.com/pub.git/+/d7647400 Update tar (3976)
 https://dart.googlesource.com/pub.git/+/98565c3e Bump actions/checkout from 3.5.2 to 3.5.3 (3960)
 https://dart.googlesource.com/pub.git/+/f323772e Summary for `pub get`, don't show unchanged in `pub upgrade` (3952)

```

Diff: https://dart.googlesource.com/pub.git/+/42819a1e10f803eb7f6296692c5a976e1c647360..be6868ba132c782d9835b1638a634ecb73428579/
Change-Id: I4b4f42790bb50ad4b17bdf2ac195494a241a63f0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/324101
Reviewed-by: Jonas Jensen <jonasfj@google.com>
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>

CHANGELOG.md

@@ -157,6 +157,14 @@ constraint][language version] lower bound to 3.2 or greater (`sdk: '^3.2.0'`).
 
 [#53106]: https://github.com/dart-lang/sdk/issues/53106
 
+#### Pub
+
+- New option `dart pub upgrade --tighten` which will update dependencies' lower
+  bounds in pubspec.yaml to match the current version.
+- The commands `dart pub get`/`add`/`upgrade` will now show if a dependency
+  changed between direct, dev and transitive dependency.
+- The command `dart pub upgrade` no longer shows unchanged dependencies.
+
 ## 3.1.0
 
 ### Libraries

DEPS

@@ -167,7 +167,7 @@ vars = {
   "path_rev": "96d9183ad4f9e48109fa8d4b8269cf75f13922dd",
   "pool_rev": "a5bee3540a2b5b3a3c34038667e7cd7bb514dc62",
   "protobuf_rev": "5e8f36b48f015532cd1165b47686b659fc8870da",
-  "pub_rev": "42819a1e10f803eb7f6296692c5a976e1c647360", # disable rev_sdk_deps.dart
+  "pub_rev": "be6868ba132c782d9835b1638a634ecb73428579", # disable rev_sdk_deps.dart
   "pub_semver_rev": "028b43506a3f7ec7f7b4673a78ba3da3d5fb138d",
   "shelf_rev": "2926f76dc0f713b46ba5d9dbc391e29c6d1521a9",
   "source_map_stack_trace_rev": "196d7bfa58ef307687907c323ab8e5fb1f382afa",