build(deps): bump php from 8.3-fpm to 8.4-fpm in /docker/php

Bumps php from 8.3-fpm to 8.4-fpm.

---
updated-dependencies:
- dependency-name: php
  dependency-type: direct:production
...

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

docker/php/Dockerfile

@@ -1,7 +1,7 @@
 # see https://medium.com/@othillo/adding-composer-to-php-docker-images-using-multi-stage-builds-2a10967ae6c1
 
 # use the official PHP image as base image
-FROM php:8.3-fpm
+FROM php:8.4-fpm
 
 RUN apt-get update && apt-get install --yes git zip