build(deps): bump php in /.github/actions/api-docs

Bumps php from 8.3.8-cli-alpine to 8.3.9-cli-alpine.

---
updated-dependencies:
- dependency-name: php
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/actions/api-docs/Dockerfile

@@ -1,4 +1,4 @@
-FROM php:8.3.8-cli-alpine
+FROM php:8.3.9-cli-alpine
 
 RUN curl -L -O https://github.com/phpDocumentor/phpDocumentor/releases/download/v3.4.1/phpDocumentor.phar
 RUN chmod +x phpDocumentor.phar