chore(deps): update websockets requirement from <8,>=7.0 to >=7.0,<9

Updates the requirements on [websockets](https://github.com/aaugustin/websockets) to permit the latest version.
- [Release notes](https://github.com/aaugustin/websockets/releases)
- [Changelog](https://github.com/aaugustin/websockets/blob/master/docs/changelog.rst)
- [Commits](python-websockets/websockets@7.0...8.1)

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

requirements.txt

@@ -2,4 +2,4 @@ pymongo==3.10.1
 mysql-connector-python==8.0.19
 requests==2.22.0
 python-twitter==3.5
-websockets>=7.0,<8
+websockets>=7.0,<9