tests: Falcon RC1 (#3662)

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==4.0.0b4
+    falcon-v4: falcon==4.0.0rc1
     falcon-latest: falcon
 
     # FastAPI