test: remove --harmony-sharedarraybuffer usage

This flag has been enabled by default since v8
7662e0634c3a057fa5d746912ee5af76e285c274.

PR-URL: #16343
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>

test/parallel/test-buffer-sharedarraybuffer.js

@@ -1,6 +1,5 @@
 /*global SharedArrayBuffer*/
 'use strict';
-// Flags: --harmony-sharedarraybuffer
 
 require('../common');
 const assert = require('assert');

test/parallel/test-util-format-shared-arraybuffer.js

@@ -1,5 +1,3 @@
-// Flags: --harmony_sharedarraybuffer
-
 'use strict';
 require('../common');
 const assert = require('assert');

test/parallel/test-v8-serdes-sharedarraybuffer.js

@@ -1,6 +1,5 @@
 /*global SharedArrayBuffer*/
 'use strict';
-// Flags: --harmony-sharedarraybuffer
 
 const common = require('../common');
 const assert = require('assert');