docs(ngInit): fix typo ("unnecesary" --> "unnecessary")

Closes #12810

Author: gkalpak

src/ng/directive/ngInit.js

@@ -10,7 +10,7 @@
  * current scope.
  *
  * <div class="alert alert-danger">
- * This directive can be abused to add unnecesary amounts of logic into your templates.
+ * This directive can be abused to add unnecessary amounts of logic into your templates.
  * There are only a few appropriate uses of `ngInit`, such as for aliasing special properties of
  * {@link ng.directive:ngRepeat `ngRepeat`}, as seen in the demo below; and for injecting data via
  * server side scripting. Besides these few cases, you should use {@link guide/controller controllers}