citemplate: rebuild the gst-build image

Need to rebuild the image cache to account for the wrap changes [1]

[1] gst-build!188

Part-of: <!340>

gitlab/ci_template.yml

@@ -21,7 +21,7 @@ variables:
   # If you are hacking on them or need a them to rebuild, its enough
   # to change any part of the string of the image you want.
   ###
-  FEDORA_TAG:  '2020-09-10.1'
+  FEDORA_TAG:  '2020-09-15.0'
   CERBERO_TAG: '2020-09-09.2'
   ANDROID_TAG: '2020-09-09.2'
   MANIFEST_TAG: '2020-06-25.0'
@@ -1099,6 +1099,10 @@ documentation:
     CI_ARTIFACTS_URL: "${CI_PROJECT_URL}/-/jobs/${CI_JOB_ID}/artifacts/raw/"
   script:
   - pip3 install --upgrade git+https://github.com/hotdoc/hotdoc@28ad9aa59daa49d6b3fd1bc6b144df52af39475b
+
+  # FIXME: remove this once the docs image is updated
+  - rm -rf /gst-build/subprojects/pygobject/
+
   - *gst_build
   - ./gst-uninstalled.py ninja -C build/ plugins_doc_caches
   - |