chore(warning): Add "symbol" and "boolean" for "key" warning

Booleans as keys are supported since vuejs#6127 and symbols since vuejs#7271.
The warning should reflect that.

Author: mpawelski

src/core/vdom/create-element.js

@@ -74,7 +74,7 @@ export function _createElement (
     if (!__WEEX__ || !('@binding' in data.key)) {
       warn(
         'Avoid using non-primitive value as key, ' +
-        'use string/number value instead.',
+        'use string/number/symbol/boolean value instead.',
         context
       )
     }