test: deflake test-webcrypto-crypto-job-mode

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
PR-URL: #63543
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: panva

test/parallel/test-webcrypto-crypto-job-mode.js

@@ -163,7 +163,7 @@ async function withObjectPrototypeSetters(names, fn) {
       { name: 'AES-CBC', iv },
       key,
       Buffer.alloc(16)));
-    ciphertext[ciphertext.length - 1] ^= 0xff;
+    ciphertext[0] ^= 0xff;
 
     await assert.rejects(
       subtle.decrypt({ name: 'AES-CBC', iv }, key, ciphertext),