Plugins page errors should use 'error' class rather than 'updated'

[dd32]

Just noticed that some errors on the plugins page are using the Informational notification colours instead of an error colour.

It makes sense that we should update these.

spotted another two cases

"No out of date plugins were selected." might as well say "All selected plugins are up to date." As in, you wanted to update plugins X, Y, and Z, and they are indeed updated. Arguably not a failure condition; it can go either way.

I agree, that particular message is worded as an error at present, but could be re-worded to be more friendly "yay, they're all up to date already" instead.

The first two cases have already been fixed in #28260.

26494.3.diff​ changes the wording of No out of date plugins were selected. to All selected plugins are up to date., keeping the notice class as it isn't really an error.

In 33983:

Plugins page: re-word "No out of date plugins were selected." to "All selected plugins are up to date." since it's not really an error condition.

Props swissspidy.
Fixes #26494.