Bump aiohttp from 3.6.2 to 3.7.4 (#266)

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] <[email protected]>

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

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ pytest==5.3.2
 python-dateutil==2.8.0
 requests==2.22.0
 jsonschema==3.2.0
-aiohttp==3.6.2
+aiohttp==3.7.4
 azure-functions>=1.2.0
 nox==2019.11.9
 furl==2.1.0