Remove deprecated IE11 Esc key case

Apparently KeyboardEvent.key is `Esc` in IE11 while other browsers use
`Escape`. After a quick check in BrowserStack, Edge 17 and 18 also use
`Escape`, so we can get rid of the `Esc` case.

app/assets/javascripts/lib/utils/keys.js

-/* eslint-disable @gitlab/require-i18n-strings */
-
 export const ESC_KEY = 'Escape';
-export const ESC_KEY_IE11 = 'Esc'; // https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key
 export const ENTER_KEY = 'Enter';

app/assets/javascripts/monitoring/components/dashboard.vue

@@ -7,7 +7,7 @@ import DashboardHeader from './dashboard_header.vue';
 import DashboardPanel from './dashboard_panel.vue';
 import { s__ } from '~/locale';
 import createFlash from '~/flash';
-import { ESC_KEY, ESC_KEY_IE11 } from '~/lib/utils/keys';
+import { ESC_KEY } from '~/lib/utils/keys';
 import { mergeUrlParams, updateHistory } from '~/lib/utils/url_utility';
 import invalidUrl from '~/lib/utils/invalid_url';
 import Icon from '~/vue_shared/components/icon.vue';
@@ -311,7 +311,7 @@ export default {
     },
     onKeyup(event) {
       const { key } = event;
-      if (key === ESC_KEY || key === ESC_KEY_IE11) {
+      if (key === ESC_KEY) {
         this.clearExpandedPanel();
       }
     },

spec/frontend/monitoring/components/dashboard_spec.js

@@ -2,7 +2,7 @@ import { shallowMount, mount } from '@vue/test-utils';
 import VueDraggable from 'vuedraggable';
 import MockAdapter from 'axios-mock-adapter';
 import { TEST_HOST } from 'helpers/test_constants';
-import { ESC_KEY, ESC_KEY_IE11 } from '~/lib/utils/keys';
+import { ESC_KEY } from '~/lib/utils/keys';
 import { objectToQuery } from '~/lib/utils/url_utility';
 import axios from '~/lib/utils/axios_utils';
 import { dashboardEmptyStates, metricStates } from '~/monitoring/constants';
@@ -566,15 +566,6 @@ describe('Dashboard', () => {
           undefined,
         );
       });
-
-      it('restores dashboard from full screen by typing the Escape key on IE11', () => {
-        mockKeyup(ESC_KEY_IE11);
-
-        expect(store.dispatch).toHaveBeenCalledWith(
-          `monitoringDashboard/clearExpandedPanel`,
-          undefined,
-        );
-      });
     });
   });