Bump open-webui/open-webui from v0.5.3 to 0.5.4 in /docker

Bumps [open-webui/open-webui](https://github.com/open-webui/open-webui) from v0.5.3 to 0.5.4.
- [Release notes](https://github.com/open-webui/open-webui/releases)
- [Changelog](https://github.com/open-webui/open-webui/blob/main/CHANGELOG.md)
- [Commits](open-webui/open-webui@v0.5.3...v0.5.4)

---
updated-dependencies:
- dependency-name: open-webui/open-webui
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

docker/webui.Dockerfile

@@ -1 +1 @@
-FROM ghcr.io/open-webui/open-webui:v0.5.3@sha256:e5c0b17626cddb96878c589ab64b0a67572b0b8d98cf9d4a10c33d2604e3126b
+FROM ghcr.io/open-webui/open-webui:0.5.4@sha256:42e8fa544facc38d731e3d516fbf478abe435bb4b80798e0934930afea6c5bab