[CLEANUP] Remove Enumerable#contains

packages/ember-runtime/lib/mixins/enumerable.js

@@ -207,36 +207,6 @@ const Enumerable = Mixin.create({
     return last;
   }).readOnly(),
 
-  /**
-    Returns `true` if the passed object can be found in the receiver. The
-    default version will iterate through the enumerable until the object
-    is found. You may want to override this with a more efficient version.
-
-    ```javascript
-    let arr = ['a', 'b', 'c'];
-
-    arr.contains('a'); // true
-    arr.contains('z'); // false
-    ```
-
-    @method contains
-    @deprecated Use `Enumerable#includes` instead. See https://emberjs.com/deprecations/v2.x#toc_enumerable-contains
-    @param {Object} obj The object to search for.
-    @return {Boolean} `true` if object is found in enumerable.
-    @public
-  */
-  contains(obj) {
-    deprecate(
-      '`Enumerable#contains` is deprecated, use `Enumerable#includes` instead.',
-      false,
-      { id: 'ember-runtime.enumerable-contains', until: '3.0.0', url: 'https://emberjs.com/deprecations/v2.x#toc_enumerable-contains' }
-    );
-
-    let found = this.find(item => item === obj);
-
-    return found !== undefined;
-  },
-
   /**
     Iterates through the enumerable, calling the passed function on each
     item. This method corresponds to the `forEach()` method defined in

packages/ember-runtime/tests/suites/enumerable.js

@@ -280,7 +280,6 @@ const EnumerableTests = Suite.extend({
 import anyTests         from './enumerable/any';
 import isAnyTests       from './enumerable/is_any';
 import compactTests     from './enumerable/compact';
-import containsTests    from './enumerable/contains';
 import includesTests    from './enumerable/includes';
 import everyTests       from './enumerable/every';
 import filterTests      from './enumerable/filter';
@@ -302,7 +301,6 @@ import withoutTests     from './enumerable/without';
 EnumerableTests.importModuleTests(anyTests);
 EnumerableTests.importModuleTests(isAnyTests);
 EnumerableTests.importModuleTests(compactTests);
-EnumerableTests.importModuleTests(containsTests);
 EnumerableTests.importModuleTests(everyTests);
 EnumerableTests.importModuleTests(filterTests);
 EnumerableTests.importModuleTests(findTests);