Revert "Add setting to use document replication for system indices. (#…

…802)"

This reverts commit 55b6968.

src/main/kotlin/org/opensearch/replication/metadata/store/ReplicationMetadataStore.kt

@@ -40,7 +40,6 @@ import org.opensearch.common.xcontent.LoggingDeprecationHandler
 import org.opensearch.core.xcontent.NamedXContentRegistry
 import org.opensearch.core.xcontent.ToXContent
 import org.opensearch.core.xcontent.XContentParser
-import org.opensearch.indices.replication.common.ReplicationType
 import org.opensearch.replication.util.suspendExecuteWithRetries
 
 class ReplicationMetadataStore constructor(val client: Client, val clusterService: ClusterService,
@@ -266,7 +265,6 @@ class ReplicationMetadataStore constructor(val client: Client, val clusterServic
                 .put(IndexMetadata.INDEX_AUTO_EXPAND_REPLICAS_SETTING.key, "0-1")
                 .put(IndexMetadata.INDEX_PRIORITY_SETTING.key, Int.MAX_VALUE)
                 .put(IndexMetadata.INDEX_HIDDEN_SETTING.key, true)
-                .put(IndexMetadata.INDEX_REPLICATION_TYPE_SETTING.key, ReplicationType.DOCUMENT) // System Indices should use Document Replication strategy
                 .build()
     }