Bump aiohttp from 3.6.2 to 3.7.3

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.6.2 to 3.7.3.
- [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...v3.7.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]