Update RELEASE to v0.54.1 (#6232) (#6237)

Signed-off-by: Yoshiki Fujikane <ffjlabo@gmail.com>
Signed-off-by: pipecd-bot <pipecd.dev@gmail.com>
Co-authored-by: Yoshiki Fujikane <40124947+ffjlabo@users.noreply.github.com>

Author: github-actions[bot]

RELEASE

@@ -1,6 +1,6 @@
 # Generated by `make release` command.
 # DO NOT EDIT.
-tag: v0.54.0
+tag: v0.54.1
 
 releaseNoteGenerator:
   showCommitter: false