Merge branch 'docs-clarify-rules-allow-failure' into 'master'

Clarify how rules:allow_failure is applied

See merge request gitlab-org/gitlab!33089

doc/ci/yaml/README.md

@@ -1048,6 +1048,10 @@ You can use [`allow_failure: true`](#allow_failure) within `rules:` to allow a j
 wait for action, without stopping the pipeline itself. All jobs using `rules:` default to `allow_failure: false`
 if `allow_failure:` is not defined.
 
+The rule-level `rules:allow_failure` option overrides the job-level
+[`allow_failure`](#allow_failure) option, and is only applied when the job is
+triggered by the particular rule.
+
 ```yaml
 job:
   script: "echo Hello, Rules!"