Correct syntax

Signed-off-by: Evili del Rio <evili@iiia.csic.es>

.gitlab-ci.yml

@@ -37,7 +37,7 @@ build_tags:
   only:
     - tags
   variables:
-    - PYTHON_VERSIONS: "3.7 3.8 3.9 3.10"
+    PYTHON_VERSIONS: "3.7 3.8 3.9 3.10"
   script:
     - for python_version in ${PYTHON_VERSIONS}
     - do