Bump composer from 2.7.9 to 2.8.0 in /docker

Bumps composer from 2.7.9 to 2.8.0.

---
updated-dependencies:
- dependency-name: composer
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

docker/Dockerfile

@@ -1,5 +1,5 @@
 # Use composer image for better caching
-FROM composer:2.7.9 AS composer-build
+FROM composer:2.8.0 AS composer-build
 COPY composer.json composer.lock ./
 RUN composer install --no-scripts