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>

requirements.txt

@@ -2,6 +2,6 @@ requests==2.22.0
 async_timeout==3.0.1
 youtube_dl==2021.2.10
 discord.py==1.5.0
-aiohttp==3.7.3
+aiohttp==3.7.4
 discord==1.0.1
 python-dotenv==0.15.0