Bump vcap_staging pointer

git shortlog:
      David Sabeti and Jennifer Hickey (1):
        Bump Java buildpack to include Play diagnostics

      Jesse Zhang (1):
        Merge "Redirect gemfile task logging to stdout"

      Jesse Zhang and Maria Shaldibina (1):
        Redirect gemfile task logging to stdout

Change-Id: Ib891f9d22075d193bb51318216d7e8b06c7f5c6b