Merge branch 'docs-update-needs-example' into 'master'

Update the syntax of DAG example

See merge request gitlab-org/gitlab-ce!32137

doc/ci/yaml/README.md

@@ -1820,19 +1820,19 @@ mac:build:
 linux:rspec:
   stage: test
-  needs: [linux:build]
+  needs: ["linux:build"]
 linux:rubocop:
   stage: test
-  needs: [linux:build]
+  needs: ["linux:build"]
 mac:rspec:
   stage: test
-  needs: [mac:build]
+  needs: ["mac:build"]
 mac:rubocop:
   stage: test
-  needs: [mac:build]
+  needs: ["mac:build"]
 production:
   stage: deploy