Update aiohttp requirement from <3.7.0,>=3.6.0 to >=3.6.0,<3.8.0 (#10)

Updates the requirements on [aiohttp](https://github.com/aio-libs/aiohttp) to permit the latest version.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst)
- [Commits](aio-libs/aiohttp@v3.6.0...v3.7.1)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

Diff for: requirements.txt

@@ -1 +1 @@
-aiohttp>=3.6.0,<3.7.0
+aiohttp>=3.6.0,<3.8.0