chore(release): re-bump v4-next to 4.4.0 (#23423)

## Summary

Re-applies the v4-next minor-cycle bump from `4.3.0` → `4.4.0`. The
original bump (#23307) was silently undone when
`pull-v4-into-v4-next.yml` fast-forwarded `v4-next` onto `v4` after the
v4.3.0 release merges.

## What happened

1. #23307 set v4-next's manifest to `4.4.0` (May 15).
2. The "merge v4-next into v4 for v4.3.0-rc.2 release" merge
(88ef5ca) resolved the manifest conflict in favor of v4's `4.3.0` —
the correct call for v4, but it left v4 ahead of v4-next on every file
except the manifest.
3. `pull-v4-into-v4-next.yml` triggered on the subsequent pushes to v4
and ran `git merge origin/v4 --no-edit` while on v4-next. Because
v4-next's tip was an ancestor of v4's tip (v4 already had v4-next as a
parent of the merge), the merge fast-forwarded v4-next to v4 —
overwriting the 4.4.0 manifest with `4.3.0`.
4. `origin/v4` and `origin/v4-next` now point to the same commit
(`54564b4d53`).

## Follow-up (separate PR)

The auto-sync workflow should preserve `.release-please-manifest.json`
from `v4-next` when merging v4 → v4-next (e.g. `git checkout --ours
.release-please-manifest.json` after the merge, or fail the workflow if
the manifest version regresses). I'll send that as a separate change.

## Test plan
- [ ] CI green
- [ ] After merge, confirm `.release-please-manifest.json` on `v4-next`
reads `4.4.0`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: aminsammara

.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "4.3.0"
+  ".": "4.4.0"
 }