Regression in Community Build: ScalaPB

[allanrenucci]

https://travis-ci.org/lampepfl/dotty-community-build/jobs/344732706

#3342 seems to be the cause of the regression

[nicolasstucki]

Fixed with #4145

[nicolasstucki]

In that PR I stop forcing types on scala2 classes. One of which contained a macro in ScalaPB.

[liufengyun]

So we can enable ScalaPB benchmarks again? I'll do it now.

[nicolasstucki]

We should be able to re-enable them