Merge pull request #721 from pikesley/dependabot/pip/gunicorn-21.2.0

Bump gunicorn from 20.1.0 to 21.2.0

Author: pikesley

requirements.txt

@@ -15,7 +15,7 @@ gitdb==4.0.11
 GitPython==3.1.41
 gpiozero==1.6.2
 greenlet==2.0.2
-gunicorn==20.1.0
+gunicorn==21.2.0
 hiredis==2.2.2
 idna==3.4
 importlib-metadata==4.8.2