Escape parentheses in Azure allocation failure regex.

PiperOrigin-RevId: 889469004

Author: jellyfishcake

perfkitbenchmarker/providers/azure/azure_kubernetes_service.py

@@ -244,7 +244,7 @@ def _CreateNodePool(self, nodepool_config: container.BaseNodePoolConfig):
     # Validity should be uncovered during development. Quota and capacity
     # will trigger failures in other VM benchmarks.
     if re.search(
-        'Allocation failed. VM(s) with the following constraints cannot be'
+        'Allocation failed. VM\\(s\\) with the following constraints cannot be'
         ' allocated, because the condition is too restrictive.',
         stderr,
     ):