AMBARI-25568 Fix The 'NodeManager RAM Utilized' metric in the heatmap had no unit (#3245)

* Update YARN_widgets.json

ambari-server/src/main/resources/common-services/YARN/2.1.0.2.0/YARN_widgets.json

@@ -577,7 +577,7 @@
             }
           ],
           "properties": {
-            "display_unit": "",
+            "display_unit": "GB",
             "max_limit": "100"
           }
         },

ambari-server/src/main/resources/stacks/HDP/2.3/services/YARN/YARN_widgets.json

@@ -636,7 +636,7 @@
             }
           ],
           "properties": {
-            "display_unit": "",
+            "display_unit": "GB",
             "max_limit": "100"
           }
         },