Bump aiohttp from 3.6.2 to 3.7.4

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.6.2 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@v3.6.2...v3.7.4)

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

Author: dependabot[bot]

requirements.freeze.txt

@@ -1,7 +1,7 @@
 afdko==3.2.0
 aiodns==2.0.0
 aiofiles==0.4.0
-aiohttp==3.6.2
+aiohttp==3.7.4
 appdirs==1.4.3
 astroid==2.3.0
 async-timeout==3.0.1