Invalidate notifier plugin cache when changing and deleting message digest interval

OK now we have a failing test. lets make it passing.

Now the test is passing. See https://git.drupalcode.org/issue/message_digest-3510956/-/pipelines/439923 (Previous major)..
There are some tests failing due to other issues e.g. errors in views settings (Not related to this change).

Here is a patch from the MR

This looks good, just running the tests only on the latest to see if they fail as expected. Thanks for putting this together with a test no-less.

Does what is on the tin ;)

bluegeek9 → changed the visibility of the branch 8.x-1.x to hidden.