Bump aiohttp from 3.7.4 to 3.9.0 (#340)

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.7.4 to 3.9.0.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst)
- [Commits](aio-libs/aiohttp@v3.7.4...v3.9.0)

---
updated-dependencies:
- dependency-name: aiohttp
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-dev.txt

@@ -1,5 +1,5 @@
 aiofiles==0.8.0
-aiohttp==3.7.4
+aiohttp==3.9.0
 async-timeout==3.0.1
 attrs==20.2.0
 bleach==3.3.0