Remove the SENTRY_ENVIRONMENT env var from config

[data-sync-user]

From: https://mozilla-hub.atlassian.net/browse/STOR-314?focusedCommentId=1139744

We still have yet to deploy the change that removes the need for a separate SENTRY_ENVIRONMENT env var. Once we’ve deployed a version or two that supports its removal to stage/prod (giving it a version or two in case we need to rollback), we should remove it from our helm charts as it will be no longer necessary.

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