Fixed incorrect fontend version concatenation

Makefile

@@ -89,7 +89,7 @@ ci@all: _download_tools ## Build all recent versions from github (Params: GIT_TA
 			RELEASE_TAG_TEMPLATE="%MATCH_0%-b${GIT_TAG}"; \
 		fi; \
 	fi; \
-	./.helpers/for-each-github-release --exec "make build_image push_image VERSION=%MATCH_0% VERSION_FRONT=%MATCH_0%-stable GIT_TAG=$$GIT_TAG" --repo-name taigaio/taiga-back --dest-docker-repo quay.io/riotkit/taiga $${BUILD_PARAMS}--allowed-tags-regexp="([0-9\.]+)$$" --release-tag-template="$${RELEASE_TAG_TEMPLATE}" --max-versions=5 --verbose
+	./.helpers/for-each-github-release --exec "make build_image push_image VERSION=%MATCH_0% VERSION_FRONT=%MATCH_0% GIT_TAG=$$GIT_TAG" --repo-name taigaio/taiga-back --dest-docker-repo quay.io/riotkit/taiga $${BUILD_PARAMS}--allowed-tags-regexp="([0-9\.]+)$$" --release-tag-template="$${RELEASE_TAG_TEMPLATE}" --max-versions=5 --verbose
 
 _download_tools:
 	curl -s https://raw.githubusercontent.com/riotkit-org/ci-utils/${RIOTKIT_UTILS_VER}/bin/extract-envs-from-dockerfile > .helpers/extract-envs-from-dockerfile