metrics: Extend expiry of some Ash.Birch metrics

Birch launched relatively recently and we'd like to maintain these
metrics a little while longer.

Use 2025-06-22 as the expiration so the date aligns with some other
existing birch metrics. In the future all these metrics can be extended
or deleted in a single batch.

Bug: 394085263
Change-Id: I8df837fad849544893783da35b44ef0d2556665b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6227959
Auto-Submit: James Cook <jamescook@chromium.org>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1415237}