docs(ngController): Fix priority value mentioned in the docs

The `@priority 500` part was missing from the ngDoc comment, thus the docs mentioned a priority of 0
(instead of the correct 500).

Closes #9070

src/ng/directive/ngController.js

@@ -23,6 +23,7 @@
  *
  * @element ANY
  * @scope
+ * @priority 500
  * @param {expression} ngController Name of a globally accessible constructor function or an
  *     {@link guide/expression expression} that on the current scope evaluates to a
  *     constructor function. The controller instance can be published into a scope property