upgrade to dijit 1.6.3 based on dependabot recommendation

Author: bbimber

jbrowse/package-lock.json

@@ -20,6 +20,7 @@
     "rimraf": "~2.6.2",
     "lodash": ">=4.17.12",
     "growl": ">=1.10.2",
-    "dojox": ">=1.16.2"
+    "dojox": ">=1.16.3",
+    "dijit": ">=1.16.3"
   }
 }