Bump aiohttp from 3.7.4.post0 to 3.8.1

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.7.4.post0 to 3.8.1.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/v3.8.1/CHANGES.rst)
- [Commits](https://github.com/aio-libs/aiohttp/compare/v3.7.4.post0...v3.8.1)

---
updated-dependencies:
- dependency-name: aiohttp
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -5,7 +5,7 @@ pandas-ta==0.3.14b
 ccxt==1.61.24
 # Pin cryptography for now due to rust build errors with piwheels
 cryptography==36.0.0
-aiohttp==3.7.4.post0
+aiohttp==3.8.1
 SQLAlchemy==1.4.27
 python-telegram-bot==13.8.1
 arrow==1.2.1