Update sbt-scalafix to 0.10.1

[andreisilviudragnea]

• Needed to update sbt-scoverage too, since org.scoverage:scalac-scoverage-plugin_2.12.16:1.4.11 does not exist
• Needed to remove Scala 2.11 support, since scalac-scoverage-plugin is not released anymore for Scala 2.11

[andreisilviudragnea]

@liancheng

[agemooij]

@liancheng it would be great if we can release a new version of this plugin so we can all get rid of this old gem:

[info] Loading external rule(s) built against an old version of Scalafix (0.9.31).
[info] This might not be a problem, but in case you run into unexpected behavior, you
[info] should try a more recent version of the rules(s) if available. If that does
[info] not help, request the rule(s) maintainer to build against Scalafix 0.10.1
[info] or later, and downgrade Scalafix to 0.9.x (x>=31) for the time being.

Thanks!