test: prepare for consistent comma-dangle lint rule

Make changes so that tests will pass when the comma-dangle settings
applied to the rest of the code base are also applied to tests.

PR-URL: https://github.com/nodejs/node/pull/37930
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Derek Lewis <DerekNonGeneric@inf.is>

test/parallel/test-buffer-backing-arraybuffer.js

@@ -20,7 +20,7 @@ for (const { length, expectOnHeap } of tests) {
     new Float32Array(length / 4),
     new Float64Array(length / 8),
     Buffer.alloc(length),
-    Buffer.allocUnsafeSlow(length)
+    Buffer.allocUnsafeSlow(length),
     // Buffer.allocUnsafe() is missing because it may use pooled allocations.
   ];