Bump websockets from 8.1 to 9.1

Bumps [websockets](https://github.com/aaugustin/websockets) from 8.1 to 9.1.
- [Release notes](https://github.com/aaugustin/websockets/releases)
- [Changelog](https://github.com/aaugustin/websockets/blob/9.1/docs/changelog.rst)
- [Commits](https://github.com/aaugustin/websockets/compare/8.1...9.1)

---
updated-dependencies:
- dependency-name: websockets
  dependency-type: indirect
...

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

requirements.txt

@@ -1,19 +1,27 @@
-aiohttp==3.6.2
+#
+# These requirements were autogenerated by pipenv
+# To regenerate from the project's Pipfile, run:
+#
+#    pipenv lock --requirements
+#
+
+-i https://pypi.python.org/simple/
 aiohttp-jinja2==1.2.0
-async-timeout==3.0.1
+aiohttp==3.6.2
+async-timeout==3.0.1; python_full_version >= '3.5.3'
 atomicwrites==1.3.0
-attrs==19.3.0
+attrs==21.2.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'
 chardet==3.0.4
 docopt==0.6.2
 hbmqtt==0.9.5
-idna==2.8
-Jinja2==2.10.3
-MarkupSafe==1.1.1
+idna==3.2; python_version >= '3.5'
+jinja2==2.10.3
+markupsafe==2.0.1; python_version >= '3.6'
 multidict==4.5.2
-passlib==1.7.2
-PyYAML==5.3b1
-six==1.13.0
+passlib==1.7.4
+pyyaml==5.3b1
+six==1.16.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
 tinydb==3.15.2
-transitions==0.7.1
-websockets==8.1
+transitions==0.8.8
+websockets==9.1
 yarl==1.3.0