Bump mypy from 0.812 to 0.910

Bumps [mypy](https://github.com/python/mypy) from 0.812 to 0.910.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.812...v0.910)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

dev-requirements.txt

@@ -1,5 +1,5 @@
 Flask>=1.1
-mypy==0.812
+mypy==0.910
 mypy-extensions>=0.4.3
 flake8>=3.7.9 
 aiohttp>=3.6.2