Test with newer Falcon version (#3653)

Author: sentrivana

tox.ini

@@ -431,7 +431,7 @@ deps =
     falcon-v2: falcon~=2.0
     falcon-v3: falcon~=3.0
     # TODO: update to 4.0 stable when out
-    falcon-v4: falcon==4.0.0b3
+    falcon-v4: falcon==4.0.0b4
     falcon-latest: falcon
 
     # FastAPI