[skip ci]Add comment for GetIndexStates in indexcoord (#13058)

Signed-off-by: Cai.Zhang <cai.zhang@zilliz.com>

internal/indexcoord/meta_table.go

@@ -277,6 +277,7 @@ func (mt *metaTable) MarkIndexAsDeleted(indexID UniqueID) error {
 	return nil
 }
 
+// GetIndexStates gets the index states from meta table.
 func (mt *metaTable) GetIndexStates(indexBuildIDs []UniqueID) []*indexpb.IndexInfo {
 	mt.lock.Lock()
 	defer mt.lock.Unlock()