Remove IE 11 deprecation banner

This banner is no longer needed because the client does not support IE
11 and aborts startup in that browser.

src/sidebar/components/hypothesis-app.js

@@ -3,7 +3,6 @@ import { useEffect, useMemo } from 'preact/hooks';
 import propTypes from 'prop-types';
 
 import bridgeEvents from '../../shared/bridge-events';
-import { isIE11 } from '../../shared/user-agent';
 import serviceConfig from '../service-config';
 import useStore from '../store/use-store';
 import uiConstants from '../ui-constants';
@@ -108,20 +107,6 @@ function HypothesisApp({
     }
   }, [isSidebar, profile, openSidebarPanel, settings]);
 
-  // Show a deprecation warning if current browser is IE11
-  useEffect(() => {
-    if (isIE11()) {
-      toastMessenger.notice(
-        'Hypothesis is ending support for this browser (Internet Explorer 11) on July 1, 2020.',
-        {
-          autoDismiss: false,
-          moreInfoURL:
-            'https://web.hypothes.is/help/which-browsers-are-supported-by-hypothesis/',
-        }
-      );
-    }
-  }, [toastMessenger]);
-
   const login = async () => {
     if (serviceConfig(settings)) {
       // Let the host page handle the login request

src/sidebar/components/test/hypothesis-app-test.js

@@ -8,7 +8,6 @@ import HypothesisApp, { $imports } from '../hypothesis-app';
 
 describe('HypothesisApp', () => {
   let fakeApplyTheme;
-  let fakeUserAgent = null;
   let fakeStore = null;
   let fakeAuth = null;
   let fakeBridge = null;
@@ -74,10 +73,6 @@ describe('HypothesisApp', () => {
       call: sinon.stub(),
     };
 
-    fakeUserAgent = {
-      isIE11: sinon.stub().returns(false),
-    };
-
     fakeToastMessenger = {
       error: sinon.stub(),
       notice: sinon.stub(),
@@ -85,7 +80,6 @@ describe('HypothesisApp', () => {
 
     $imports.$mock(mockImportedComponents());
     $imports.$mock({
-      '../../shared/user-agent': fakeUserAgent,
       '../service-config': fakeServiceConfig,
       '../store/use-store': callback => callback(fakeStore),
       '../util/session': {
@@ -147,24 +141,6 @@ describe('HypothesisApp', () => {
     });
   });
 
-  describe('toast message warning of IE11 deprecation', () => {
-    it('shows notice if user agent is IE11', () => {
-      fakeUserAgent.isIE11.returns(true);
-
-      createComponent();
-
-      assert.called(fakeToastMessenger.notice);
-    });
-
-    it('does not show notice if another user agent', () => {
-      fakeUserAgent.isIE11.returns(false);
-
-      createComponent();
-
-      assert.notCalled(fakeToastMessenger.notice);
-    });
-  });
-
   describe('"status" field of "auth" prop passed to children', () => {
     const getStatus = wrapper => wrapper.find('TopBar').prop('auth').status;