Updated the pattern to accomodate the previously created resources (#26213)

Author: sushantyadav-msft

specification/workloads/resource-manager/Microsoft.Workloads/SAPVirtualInstance/preview/2023-10-01-preview/SAPVirtualInstance.json

@@ -4417,7 +4417,7 @@
       "in": "path",
       "required": true,
       "type": "string",
-      "pattern": "^[A-Z][A-Z0-9]{2}$",
+      "pattern": "^[a-zA-Z][a-zA-Z0-9]{2}$",
       "description": "The name of the Virtual Instances for SAP solutions resource",
       "x-ms-parameter-location": "method"
     },