Bump arrow from 0.14.7 to 0.15.1

Bumps [arrow](https://github.com/arrow-py/arrow) from 0.14.7 to 0.15.1.
- [Release notes](https://github.com/arrow-py/arrow/releases)
- [Changelog](https://github.com/arrow-py/arrow/blob/master/CHANGELOG.rst)
- [Commits](arrow-py/arrow@0.14.7...0.15.1)

---
updated-dependencies:
- dependency-name: arrow
  dependency-type: direct:production
...

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