fix(deps): gunicorn 23 has vulnerability fixes that seem worthwhile

requirements.api.txt

@@ -1,6 +1,6 @@
 # These are dependencies required by the production Web API
 # gunivorn is only available on *nix, but it's only required for production deployments
-gunicorn>=22.0.0
+gunicorn>=23.0.0
 # uvicorn works on all platforms and is required for both dev and prod deployments
 uvicorn>=0.30.1
 # For deployment on Heroku, we want the latest g2p off GitHub