Update Go version build tags

None of the dependencies have changed in 1.15. It may be possible to simplify
some of the wrappers in rawfile following 1.13, but that can come in a later
change.

PiperOrigin-RevId: 313863264
5 files changed
tree: 0f93ebbf2c73fbf6a94916145e4f5f18b3816281
  1. pkg/
  2. AUTHORS
  3. go.mod
  4. go.sum
  5. LICENSE