Revert "Merge branch '501411-use-lowercase-cc-headers' into 'master' "

Purpose of revert

1. Duo Workflow started to fail with "failed to execute runner: error receiving event: rpc error: code = Unauthenticated desc = Header mismatch 'X-Gitlab-Realm'"
2. This is because Language Server expects headers capitalized, but this recent change converted them to lowercase.
3. The proper fix will be handled in the language server, however, until then, this is a quick fix to make Duo Workflow in the running state.

Original MR: !185072 (merged)

Checklist

• Create an issue to reinstate the merge request and assign it to the author of the reverted merge request.
• If the revert is to resolve a broken 'master' incident, please read through the Responsibilities of the Broken master resolution DRI.
• If the revert involves a database migration, please read through Deleting existing migrations.
• Add the appropriate labels before the MR is created. We can skip CI/CD jobs only if the labels are added before the CI/CD pipeline is created.

Milestone info

• I am reverting something in the current milestone. No changelog is needed, and I've added a ~"regression:*" label.
• I am reverting something in a different milestone. A changelog is needed, and I've removed the ~"regression:*" label.

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