Update bookworm's dependencies

structlog 22.3.0 migrated just now, and prometheus_client 0.16.0 is on its
way, to be migrated in a couple of days. Update tox.ini to test with
these versions.

Author: paravoid

tox.ini

@@ -26,8 +26,8 @@ deps =
 
 [testenv:py311-bookworm]
 deps =
-    prometheus_client==0.9.0
-    structlog==20.1.0
+    prometheus_client==0.16.0
+    structlog==22.3.0
     {[testenv]deps}
 
 [testenv:coverage]