[ package:dtd ] Prepare for 2.5.1 release

Change-Id: Ia0fac45cf97306a38dfb5fe36c732c98df9568ed
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/422861
Auto-Submit: Ben Konyi <bkonyi@google.com>
Commit-Queue: Derek Xu <derekx@google.com>
Reviewed-by: Derek Xu <derekx@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dtd/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 2.5.1-wip
+## 2.5.1
 
 - Widen the dependency on `unified_analytics` to include 8.0.0.
 

pkg/dtd/pubspec.yaml

@@ -1,5 +1,5 @@
 name: dtd
-version: 2.5.1-wip
+version: 2.5.1
 description: A package for communicating with the Dart Tooling Daemon.
 repository: https://github.com/dart-lang/sdk/tree/main/pkg/dtd