Update Mattermost test for settings changes

Summary

Currently pipelines will (inconsistently) fail on the system console/settings change test. This test was originally designed to test and validate that settings changes are saved (which utilizes the database storage).

Steps to reproduce

Run a pipeline a couple times and you'll hit this error likely. (Also see relevant logs for example)

What is the current behavior?

Test is not consistent in its behavior, causing erroneous failures.

What is the expected behavior?

Test should work consistently, only fail when there are real issues.

Relevant logs and/or screenshots

https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/jobs/5993517

Path forward

Evaluate what is happening with this test: Test originally set the Mattermost name and refreshed the page to validate that the site title updated to include that string. Potentially there is a delay in when MM updates the site title or they have changed how this setting works.

Evaluate the need for this test: As mentioned this test was originally meant to validate DB connectivity primarily. DB connectivity is also tested by chatting (which is covered in one of the other tests). Evaluate whether this test can just be removed or if there is value in checking settings changes. Remove the test if determined of little value.

(If test is of value) Evaluate if there is a better test of settings changes: See if there are other obvious settings that update something user facing and would be easy to check if they take effect. Update the test if another option is discovered.