Add version link and fix core only badge

doc/ci/yaml/README.md

@@ -3586,10 +3586,11 @@ job split into three separate jobs.
 Use `matrix:` to configure different variables for jobs that are running in parallel.
 There can be from 2 to 50 jobs.
 
-In GitLab 13.5 and later, you can have one-dimensional matrices with a single job.
+[In GitLab 13.5](https://gitlab.com/gitlab-org/gitlab/-/issues/26362) and later,
+you can have one-dimensional matrices with a single job.
 The ability to have one-dimensional matrices is [deployed behind a feature flag](../../user/feature_flags.md),
 disabled by default. It's disabled on GitLab.com. To use it in a GitLab self-managed
-instance, ask a GitLab administrator to [enable the `one_dimensional_matrix:` feature flag](../../administration/feature_flags.md). **(CORE-ONLY)**
+instance, ask a GitLab administrator to [enable the `one_dimensional_matrix:` feature flag](../../administration/feature_flags.md). **(CORE ONLY)**
 
 Every job gets the same `CI_NODE_TOTAL` [environment variable](../variables/README.md#predefined-environment-variables) value, and a unique `CI_NODE_INDEX` value.