Resolve errors from enabling drift detection for Mattermost (not operator)

Summary

Error after setting driftDetection: mode: warn or enabled

Steps to reproduce

(How one can reproduce the issue - this is very important)

What is the current behavior?

(What actually happens)

What is the expected behavior?

(What you should see instead)

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's very hard to read otherwise.)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)

/cc {put CODEOWNERs @githandles here}