[EuiDragDropContext] Convert from Enzyme to RTL

- remove unnecessary/unused jest mock

src/components/drag_and_drop/__snapshots__/drag_drop_context.test.tsx.snap

@@ -1,3 +1,3 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`EuiDragDropContext is rendered 1`] = `<div />`;
+exports[`EuiDragDropContext renders 1`] = `<div />`;

src/components/drag_and_drop/drag_drop_context.test.tsx

@@ -7,59 +7,40 @@
  */
 
 import React from 'react';
-import { mount, ReactWrapper } from 'enzyme';
-
-import { findTestSubject } from '../../test';
+import { render } from '../../test/rtl';
 import { requiredProps } from '../../test/required_props';
 
-import { EuiDragDropContext } from './';
-import { EuiDragDropContextContext } from './drag_drop_context';
-
-function snapshotDragDropContext(component: ReactWrapper) {
-  // Get the Portal's sibling and return its html
-  const renderedHtml = component.html();
-  const container = document.createElement('div');
-  container.innerHTML = renderedHtml;
-  return container.firstChild;
-}
+import {
+  EuiDragDropContext,
+  EuiDragDropContextContext,
+} from './drag_drop_context';
 
 describe('EuiDragDropContext', () => {
-  test('is rendered', () => {
-    const handler = jest.fn();
-    const component = mount(
-      <EuiDragDropContext onDragEnd={handler} {...requiredProps}>
+  it('renders', () => {
+    const { container } = render(
+      <EuiDragDropContext onDragEnd={() => {}} {...requiredProps}>
         <div />
       </EuiDragDropContext>
     );
 
-    expect(snapshotDragDropContext(component)).toMatchSnapshot();
+    expect(container.firstChild).toMatchSnapshot();
   });
 
-  describe('custom behavior', () => {
-    describe('isDraggingType', () => {
-      test('is set on proprietary context', () => {
-        jest.mock('react', () => {
-          const react = jest.requireActual('react');
-          return {
-            ...react,
-            useLayoutEffect: react.useEffect,
-          };
-        });
-        const handler = jest.fn();
-        const component = mount(
-          <EuiDragDropContext onDragEnd={handler} {...requiredProps}>
-            <EuiDragDropContextContext.Consumer>
-              {(value) => (
-                <div data-test-subj="child">
-                  {value.hasOwnProperty('isDraggingType') ? 'true' : 'false'}
-                </div>
-              )}
-            </EuiDragDropContextContext.Consumer>
-          </EuiDragDropContext>
-        );
-
-        expect(findTestSubject(component, 'child').text()).toBe('true');
-      });
+  describe('isDraggingType', () => {
+    test('is set on proprietary context', () => {
+      const { getByTestSubject } = render(
+        <EuiDragDropContext onDragEnd={() => {}}>
+          <EuiDragDropContextContext.Consumer>
+            {(value) => (
+              <div data-test-subj="child">
+                {value.hasOwnProperty('isDraggingType') ? 'true' : 'false'}
+              </div>
+            )}
+          </EuiDragDropContextContext.Consumer>
+        </EuiDragDropContext>
+      );
+
+      expect(getByTestSubject('child')).toHaveTextContent('true');
     });
   });
 });