[matter_yamltests] Properly convert wait values from str to int if necessary in the WaitFor command (#26541)

Author: vivien-apple

scripts/py_matter_yamltests/matter_yamltests/pseudo_clusters/clusters/delay_commands.py

@@ -58,7 +58,7 @@ async def WaitForMs(self, request):
                 duration_in_ms = argument['value']
 
         sys.stdout.flush()
-        time.sleep(duration_in_ms / 1000)
+        time.sleep(int(duration_in_ms) / 1000)
 
     async def WaitForMessage(self, request):
         AccessoryServerBridge.waitForMessage(request)