Update put_synonyms api specification (#2789)

Author: Samiul-TheSoccerFan

output/schema/schema.json

@@ -37,6 +37,6 @@ export interface Request extends RequestBase {
     /**
      * The synonym set information to update
      */
-    synonyms_set: SynonymRule[]
+    synonyms_set: SynonymRule | SynonymRule[]
   }
 }