Merge branch...

Merge branch 'docs/12733-docs-using-multiple-extends-in-gitlab-ci-yml-introduced-in-gitlab-12' into 'master'

Specify what version of multiple extends in docs

Closes gitlab-ee#12733

See merge request gitlab-org/gitlab-ce!30667

doc/ci/yaml/README.md

@@ -2221,10 +2221,10 @@ spinach:
   script: rake spinach
 ```
 
-It's also possible to use multiple parents for `extends`.
-The algorithm used for merge is "closest scope wins", so keys
-from the last member will always shadow anything defined on other levels.
-For example:
+In GitLab 12.0 and later, it's also possible to use multiple parents for
+`extends`.  The algorithm used for merge is "closest scope wins", so
+keys from the last member will always shadow anything defined on other
+levels.  For example:
 
 ```yaml
 .only-important: