refactor: removed IE and MS Edge Legacy leftovers from test\client\fixtures (#7960)

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## Purpose
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## Approach
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## Pre-Merge TODO
- [ ] Write tests for your proposed changes
- [ ] Make sure that existing tests do not fail

Author: Aleksey28

test/client/fixtures/core/array-utils-test.js

@@ -1,6 +1,3 @@
-const hammerhead   = window.getTestCafeModule('hammerhead');
-const browserUtils = hammerhead.utils.browser;
-
 const testCafeCore = window.getTestCafeModule('testCafeCore');
 const arrayUtils   = testCafeCore.arrayUtils;
 
@@ -139,11 +136,9 @@ test('isArray()', function () {
 test('from()', function () {
     deepEqual(arrayUtils.from('foo'), ['f', 'o', 'o']);
 
-    if (!browserUtils.isIE) {
-        deepEqual(arrayUtils.from(array, function (x) {
-            return x + x;
-        }), [2, 4, 6, 8, 10]);
-    }
+    deepEqual(arrayUtils.from(array, function (x) {
+        return x + x;
+    }), [2, 4, 6, 8, 10]);
 });
 
 test('find()', function () {

test/client/fixtures/core/dom-utils-test.js

@@ -1,10 +1,8 @@
-const hammerhead    = window.getTestCafeModule('hammerhead');
-const browserUtils  = hammerhead.utils.browser;
 const testCafeCore  = window.getTestCafeModule('testCafeCore');
 const domUtils      = testCafeCore.domUtils;
 
 asyncTest('isIFrameWindowInDOM', function () {
-    expect(browserUtils.isIE ? 2 : 1);
+    expect(1);
 
     let messageCounter = 0;
 
@@ -17,15 +15,10 @@ asyncTest('isIFrameWindowInDOM', function () {
         if (messageCounter === 0) {
             equal(event.data, 'true');
 
-            const iFramePostMessage = iframe.contentWindow.postMessage.bind(iframe.contentWindow);
-
             document.body.removeChild(iframe);
 
             //NOTE: In WebKit, scripts cannot be executed in a removed iframe. Therefore, the test is finished here.
-            if (browserUtils.isIE)
-                iFramePostMessage('isIFrameWindowInDOM', '*');
-            else
-                finishTest();
+            finishTest();
         }
         else {
             equal(event.data, 'false');

test/client/fixtures/driver/script-execution-barrier-test.js

@@ -87,16 +87,12 @@ $(document).ready(function () {
             const emitter = new ScriptExecutionEmitter();
             const barrier = new ScriptExecutionBarrier(emitter);
 
-            let scriptCounter = 0;
-
             window.stopAppending      = false;
             window.appendCustomScript = function () {
                 const script        = document.createElement('script');
                 const scriptContent = encodeURIComponent('if(!window.stopAppending)window.appendCustomScript()');
 
-                // HACK: we should request different URLs to avoid caching of response in IE 10
-                script.src = '/xhr-test/' + scriptCounter + '?expectedResponse=' + scriptContent;
-                scriptCounter++;
+                script.src = '/xhr-test/50?expectedResponse=' + scriptContent;
 
                 document.body.appendChild(script);
             };