Remove remaining uses of FormattableMarkup in Functional test assertions

I didn't find any more instances in the assertion message, so time for review.

Seems like good replacements to me.

NW for some nits.

Accepted suggestions and rebased.

Submitted a review but it seems to be the same stuff @longwave already suggested and was apparently fixed, so maybe a rebase went wrong?

@mstrelan, thanks for noticing. I don't know what I did wrong but this should include the requested changes.

I think something weird may have been going on. You were maybe the third person who mentioned pushing and it didn't appear.

But feedback appears to be addressed

Committed 3958ddc and pushed to 11.x. Thanks!

longwave → closed merge request !11486

Automatically closed - issue fixed for 2 weeks with no activity.