Un-exclude scalapb from scalameta dependency on 2.11.
Un-exclude scalapb from scalameta dependency on 2.11.

Previously, we excluded the scalapb dependency to avoid un-unused bloat
in Scalafmt. With a recent change in Scalameta some extension methods
for the `Position` class now references ScalaPB generated `s.Range`
definitions. Scala 2.12 is able to ignore the missing symbols since
they're not needed at runtime, but Scala 2.11 complains about the
missing symbols.

scalameta/scalafmt,scalameta/scalafmt,olafurpg/scalafmt,olafurpg/scalafmt,scalameta/scalafmt,olafurpg/scalafmt,scalameta/scalafmt,olafurpg/scalafmt