Fix working-dir for composer + in image build

  from "--working-dir=/usr/src/roundcubemail/"
  to "--working-dir=/var/www/html/

.gitlab-ci.yml

@@ -2,7 +2,7 @@ image: docker:24
 
 variables:
   DOCKER_TLS_CERTDIR: "/certs"
-  BUILD_VERSION: p5
+  BUILD_VERSION: p6
 
 services:
   - docker:24-dind

Dockerfile

@@ -8,7 +8,7 @@ RUN set -ex; \
     ; \
     \
     composer \
-        --working-dir=/usr/src/roundcubemail/ \
+        --working-dir=/var/www/html/plugins \
         --prefer-dist \
         --prefer-stable \
         --update-no-dev \