Update default value of Section4dAWSMetricsTagFilters mp test yaml

Author: himsharma01

aws-observability/templates/sumologic_observability.mp.test.yaml

@@ -241,7 +241,7 @@ Parameters:
     Type: String
     AllowedPattern: '^\{.*\}$'
     Description: "Provide JSON format of the namespaces with it's tags values to add filters to your metrics. Use semicolons to separate multiple values for the same tag key. AWS Tag Filters will be added to the Source. For JSON format sample, visit <#TODO>"
-    Default: {}
+    Default: "{}"
 
   Section5aAutoEnableS3LogsALBResourcesOptions:
     Type: String