chore(buildpacks): update heroku-buildpack-scala to v77

See heroku/heroku-buildpack-scala@v76...v77

Author: mboersma

rootfs/builder/install-buildpacks

@@ -39,4 +39,4 @@ download_buildpack https://github.com/heroku/heroku-buildpack-php.git
 download_buildpack https://github.com/heroku/heroku-buildpack-play.git           v26      09-play
 download_buildpack https://github.com/heroku/heroku-buildpack-python.git         v109     10-python
 download_buildpack https://github.com/heroku/heroku-buildpack-ruby.git           v167     11-ruby
-download_buildpack https://github.com/heroku/heroku-buildpack-scala.git          v76      12-scala
+download_buildpack https://github.com/heroku/heroku-buildpack-scala.git          v77      12-scala