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

@@ -154,10 +154,10 @@ function testUint(clazz) {
       type: RangeError,
       message: /^The value "[^"]*" is invalid for option "value"$/
     }, 2);
-    assert.throws(function() {
+    assert.throws(() => {
       data.writeUIntBE(val, 0, i);
     }, errMsg);
-    assert.throws(function() {
+    assert.throws(() => {
       data.writeUIntLE(val, 0, i);
     }, errMsg);
     val *= 0x100;