Revert iOS keyup workaround

It seems Apple has fixed their buggy keyup events, so remove the
workaround and allow keys to be kept pressed again.

This is a revert of 9e99ce126ca8f6f350fa015c0e58d35103c62f7e.

kasmweb/core/input/keyboard.js

@@ -118,9 +118,7 @@ export default class Keyboard {
 
         // We cannot handle keys we cannot track, but we also need
         // to deal with virtual keyboards which omit key info
-        // (iOS omits tracking info on keyup events, which forces us to
-        // special treat that platform here)
-        if ((code === 'Unidentified') || browser.isIOS()) {
+        if (code === 'Unidentified') {
             if (keysym) {
                 // If it's a virtual keyboard then it should be
                 // sufficient to just send press and release right

kasmweb/tests/test.keyboard.js

@@ -175,54 +175,6 @@ describe('Key Event Handling', function () {
             };
             kbd._handleKeyDown(keyevent('keydown', {code: 'Unidentified', key: 'a'}));
         });
-
-        describe('iOS', function () {
-            let origNavigator;
-            beforeEach(function () {
-                // window.navigator is a protected read-only property in many
-                // environments, so we need to redefine it whilst running these
-                // tests.
-                origNavigator = Object.getOwnPropertyDescriptor(window, "navigator");
-                if (origNavigator === undefined) {
-                    // Object.getOwnPropertyDescriptor() doesn't work
-                    // properly in any version of IE
-                    this.skip();
-                }
-
-                Object.defineProperty(window, "navigator", {value: {}});
-                if (window.navigator.platform !== undefined) {
-                    // Object.defineProperty() doesn't work properly in old
-                    // versions of Chrome
-                    this.skip();
-                }
-
-                window.navigator.platform = "iPhone 9.0";
-            });
-            afterEach(function () {
-                Object.defineProperty(window, "navigator", origNavigator);
-            });
-
-            it('should fake keyup events on iOS', function (done) {
-                if (browser.isIE() || browser.isEdge()) this.skip();
-                let count = 0;
-                const kbd = new Keyboard(document);
-                kbd.onkeyevent = (keysym, code, down) => {
-                    switch (count++) {
-                        case 0:
-                            expect(keysym).to.be.equal(0x61);
-                            expect(code).to.be.equal('KeyA');
-                            expect(down).to.be.equal(true);
-                            break;
-                        case 1:
-                            expect(keysym).to.be.equal(0x61);
-                            expect(code).to.be.equal('KeyA');
-                            expect(down).to.be.equal(false);
-                            done();
-                    }
-                };
-                kbd._handleKeyDown(keyevent('keydown', {code: 'KeyA', key: 'a'}));
-            });
-        });
     });
 
     describe('Track Key State', function () {