fix riot-web version strip

roles/matrix-riot-web/tasks/setup_riot_web.yml

@@ -28,7 +28,7 @@
   git:
     repo: https://github.com/vector-im/riot-web.git
     dest: "{{ matrix_riot_web_docker_src_files_path }}"
-    version: "v{{ matrix_riot_web_docker_image.split(':')[1] }}"
+    version: "{{ matrix_riot_web_docker_image.split(':')[1] }}"
     force: "yes"
   when: "matrix_riot_web_enabled|bool and matrix_riot_web_self_build"