docs($provide): add array annotation type to $provide.decorator parameter

The $provide.decorator function, as per the documentation, "is called using
the auto.injector.invoke method and is therefore fully injectable."

The current @param contradicts this by stating that only a functions may
be used as an argument.

Closes angular#11507

Author: KevinBrogan

src/auto/injector.js

@@ -593,7 +593,7 @@ function annotate(fn, strictDi, name) {
  * object which replaces or wraps and delegates to the original service.
  *
  * @param {string} name The name of the service to decorate.
- * @param {function()} decorator This function will be invoked when the service needs to be
+ * @param {Function|Array} decorator This function will be invoked when the service needs to be
  *    instantiated and should return the decorated service instance. The function is called using
  *    the {@link auto.$injector#invoke injector.invoke} method and is therefore fully injectable.
  *    Local injection arguments: