Update stale link

lib/gitlab/ci/templates/Python.gitlab-ci.yml

@@ -13,7 +13,7 @@ variables:
   PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
 
 # Pip's cache doesn't store the python packages
-# https://pip.pypa.io/en/stable/reference/pip_install/#caching
+# https://pip.pypa.io/en/stable/topics/caching/
 #
 # If you want to also cache the installed packages, you have to install
 # them in a virtualenv and cache it as well.