Bump aiohttp from 3.6.3 to 3.7.4

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.6.3 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](aio-libs/aiohttp@v3.6.3...v3.7.4)

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

requirements.txt

@@ -1,5 +1,5 @@
 aiodns==2.0.0
-aiohttp==3.6.3
+aiohttp==3.7.4
 aiohttp-requests==0.1.3
 astunparse==1.6.3
 async-timeout==3.0.1