Use blacklist for tests for Scala.js
Use blacklist for tests for Scala.js

Since the blacklist-based approach makes it easier to enable new tests
this patch replaces the whitelist-based approach for enabling tests for
Scala.js with the blacklist-based approach for the following groups:

- testsuite/junit
- testsuite/niobuffer

Signed-off-by: Nikita Eshkeev <e441a4fb4862099ee4a340d52496345088acaa5f@gmail.com>

som-snytt/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,dotty-staging/dotty,lampepfl/dotty,som-snytt/dotty,sjrd/dotty,sjrd/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,som-snytt/dotty