Rename section header to be more clear

doc/ci/merge_request_pipelines/index.md

@@ -56,7 +56,7 @@ The same tag is shown on the pipeline's details:
 ![Pipeline's details](img/pipeline_detail.png)
-## Making all jobs run for your MR pipelines 
+## Having all jobs always run, except for a few
 The behavior of the `only: merge_requests` rule is such that _only_ jobs with
 that rule are run in the context of a merge request; no other jobs will be run.