test: use arrow function

PR-URL: #17318
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-writeuint.js

@@ -150,10 +150,10 @@ function testUint(clazz) {
   // Test 0 to 5 bytes.
   for (let i = 0; i <= 5; i++) {
     const errmsg = `byteLength: ${i}`;
-    assert.throws(function() {
+    assert.throws(() => {
       data.writeUIntBE(val, 0, i);
     }, /"value" argument is out of bounds/, errmsg);
-    assert.throws(function() {
+    assert.throws(() => {
       data.writeUIntLE(val, 0, i);
     }, /"value" argument is out of bounds/, errmsg);
     val *= 0x100;