Bump aiohttp from 3.6.2 to 3.7.2 (#409)

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.6.2 to 3.7.2.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst)
- [Commits](aio-libs/aiohttp@v3.6.2...v3.7.2)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -1,5 +1,5 @@
 cherry_picker==1.3.2
-aiohttp==3.6.2
+aiohttp==3.7.2
 gidgethub==4.1.1
 cachetools==4.1.1
 redis==3.5.3