Bump aiohttp from 3.5.4 to 3.7.4

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.5.4 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/v3.5.4...v3.7.4)

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

requirements.txt

@@ -1,3 +1,3 @@
-aiohttp==3.5.4
+aiohttp==3.7.4
 sqlalchemy==1.3.13
 tornado==6.0.2