Renable the InvalidMessages test

[evan-forbes]

the TestReactorInvalidMessages is really really useful and critical for security but takes a long time to avoid flakes in CI

it was temporarily disabled, we either need to increase the CI resources or move this to the nightlies

[rach-id]

I think we're at a point where we're sacrificing tests just because we don't want to spend time moving core and app CI to larger servers. Probably this is the right time to do that