scrooge: Allow failures for Scala 2.13.1 for TravisCI builds
scrooge: Allow failures for Scala 2.13.1 for TravisCI builds

Problem

Much like TwitterServer, Scrooge needs Finagle dependencies
to be built in order to fully build. However, since Finagle
is not fully on Scala 2.13 yet, when trying to build Finagle
dependencies for Scala 2.13 we end up trying to resolve
Scala 2.12 dependencies. Due to how TravisCI caches by Scala
version, these dependencies are not resolvable and the build
fails.

Solution

Until Finagle is fully on Scala 2.13, let's add building for
Scala 2.13.1 to the allowed failures matrix in order to prevent
the entire TravisCI build from being marked failure.

Differential Revision: https://phabricator.twitter.biz/D445597

twitter/scrooge,twitter/scrooge,twitter/scrooge,twitter/scrooge