replace hidden keys for hidden jobs

doc/ci/yaml/README.md

@@ -756,7 +756,7 @@ Note that `script: rake test` has been overwritten by `script: rake rspec`.
 
 If you do want to include the `rake test`, see [`before_script` and `after_script`](#before_script-and-after_script).
 
-`.tests` in this example is a [hidden key](#hide-jobs), but it's
+`.tests` in this example is a [hidden job](#hide-jobs), but it's
 possible to inherit from regular jobs as well.
 
 `extends` supports multi-level inheritance, however it's not recommended to
@@ -3595,7 +3595,7 @@ Read more about the various [YAML features](https://learnxinyminutes.com/docs/ya
 
 YAML has a handy feature called 'anchors', which lets you easily duplicate
 content across your document. Anchors can be used to duplicate/inherit
-properties, and is a perfect example to be used with [hidden keys](#hide-jobs)
+properties, and is a perfect example to be used with [hidden jobs](#hide-jobs)
 to provide templates for your jobs.
 
 The following example uses anchors and map merging. It will create two jobs,
@@ -3709,7 +3709,7 @@ test:mysql:
     - ruby
 ```
 
-You can see that the hidden keys are conveniently used as templates.
+You can see that the hidden jobs are conveniently used as templates.
 
 NOTE: **Note:**
 You can't use YAML anchors across multiple files when leveraging the [`include`](#include)
@@ -3807,7 +3807,7 @@ GitLab CI/CD. In the following example, `.hidden_job` will be ignored:
 ```
 
 Use this feature to ignore jobs, or use the
-[special YAML features](#special-yaml-features) and transform the hidden keys
+[special YAML features](#special-yaml-features) and transform the hidden jobs
 into templates.
 
 ## Skip Pipeline