CHANGELOG.md: move changes from unreleased to v0.54.0

Due to a transient error encountered in release, the release v0.54.0
heading is not added successfully to the change log. This CL manually
inserted that heading.

See CL 789300

Change-Id: I4813bb6e6928d5b0a0d16dee4acf793614579126
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/790140
Auto-Submit: Hongxiang Jiang <hxjiang@golang.org>
Reviewed-by: Madeline Kalil <mkalil@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c9ed38..a788190 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,19 @@
 
 ## Unreleased
 
+## v0.55.0 (prerelease)
+
+Date: 2026-06-10
+
+This is the [pre-release version](https://code.visualstudio.com/api/working-with-extensions/publishing-extension#prerelease-extensions) of v0.56.
+
+**Full Changelog**: https://github.com/golang/vscode-go/compare/v0.54.0-rc.1...v0.55.0
+**Milestone**: https://github.com/golang/vscode-go/issues?q=milestone%3Av0.56.0
+
+## v0.54.0
+
+Date: 2026-06-10
+
 ### Changes
 
 * Interactive code actions: Support has been added for interactive refactorings that prompt the user for input before proceeding. This enables more sophisticated code actions that require user choices like "add/remove tags to struct fields", "implement interface".
@@ -17,15 +30,6 @@
 
 * In the Package Outline view, added support for following the cursor and sorting by name or position.
 
-## v0.55.0 (prerelease)
-
-Date: 2026-06-10
-
-This is the [pre-release version](https://code.visualstudio.com/api/working-with-extensions/publishing-extension#prerelease-extensions) of v0.56.
-
-**Full Changelog**: https://github.com/golang/vscode-go/compare/v0.54.0-rc.1...v0.55.0
-**Milestone**: https://github.com/golang/vscode-go/issues?q=milestone%3Av0.56.0
-
 ## v0.53.1 (prerelease)
 
 Date: 2026-01-27