Bump tensorflow-hub from 0.13.0 to 0.15.0

Bumps [tensorflow-hub](https://github.com/tensorflow/hub) from 0.13.0 to 0.15.0.
- [Release notes](https://github.com/tensorflow/hub/releases)
- [Changelog](https://github.com/tensorflow/hub/blob/master/RELEASE.md)
- [Commits](tensorflow/hub@v0.13.0...v0.15.0)

---
updated-dependencies:
- dependency-name: tensorflow-hub
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>