Bump aiohttp from 3.7.3 to 3.7.4

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.7.3 to 3.7.4.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst)
- [Commits](https://github.com/aio-libs/aiohttp/compare/v3.7.3...v3.7.4

)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

-aiohttp==3.7.3
+aiohttp==3.7.4
 asgiref==3.2.10
 async-timeout==3.0.1
 attrs==20.3.0