Consider relaxing the rule for always saying "MirrorMaker 2"

[TibsAtWork]

We currently have a Vale rule that makes sure that we always use "MirrorMaker 2", and don't allow "MirrorMaker" (see .github/vale/styles/Aiven/common_replacements.yml).

We could consider replacing that with a rule that (at least) the first usage of "MirrorMaker" must be "MirrorMaker 2", as we do for registered trademark names.