OpenSearch KNN_circuit_limit description changes (#1105)

Author: shivamp296

specification/resources/databases/models/advanced_config/opensearch_advanced_config.yml

@@ -296,10 +296,11 @@ properties:
     default: true
   knn_memory_circuit_breaker_limit:
     description: >-
-      Maximum amount of memory that can be used for KNN index, as a percentage of the JVM heap size.
+      Maximum amount of memory in percentage that can be used for the KNN index. Defaults to 50% of the JVM heap size. 
+      0 is used to set it to null which can be used to invalidate caches.
     type: integer
     example: 60
-    minimum: 3
+    minimum: 0
     maximum: 100
     default: 50
   keep_index_refresh_interval: