remove CI altogether for maintenance branch

.gitlab-ci.yml

-pylint_check:
-  image: gitlab-registry.cern.ch/atlas-tdaq-software/tdaq_ci:trigger
-  tags:
-    - tdaq
-  script:
-    - source /afs/cern.ch/atlas/project/tdaq/cmake/cmake_tdaq/bin/cm_setup.sh
-    - export PYTHONPATH="$PWD/mailinglogger:$PYTHONPATH"
-    - pylint $(find Script/ -name '*.py' -a -not -name config.py) || exit 1