Bump aiohttp from 3.7.4 to 3.7.4.post0 (#441)

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.7.4 to 3.7.4.post0.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst)
- [Commits](aio-libs/aiohttp@v3.7.4...v3.7.4.post0)

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==3.7.4
+aiohttp==3.7.4.post0
 gidgethub==5.0.0
 cachetools==4.2.1
 redis==3.5.3