test: deflake node-api test-free-called

`node-api/test_worker_buffer_callback/test-free-called` checks that
`getFreeCallCount()` is 0 on a line that runs after `new Worker()`. The
worker thread can load the addon and run its finalizer before the main
thread reaches that line, in which case the counter is already 1 and the
assertion fails. The zero check is only a baseline, so it does not need
the worker to exist.

Move it above the worker creation. The equivalent test under
test/addons/worker-buffer-callback was changed the same way in
64f7d0e.

Signed-off-by: Christian Aurich <christian.aurichzm@gmail.com>
PR-URL: #65948
Refs: #51013
Refs: https://github.com/nodejs/reliability/blob/e457f5b68957d1502256488977bc33b4346d8a4b/reports/2026-09-10.md
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Author: christianaurichzm

test/node-api/test_worker_buffer_callback/test-free-called.js

@@ -6,12 +6,13 @@ const { Worker } = require('worker_threads');
 const binding = path.resolve(__dirname, `./build/${common.buildType}/binding`);
 const { getFreeCallCount } = require(binding);
 
+assert.strictEqual(getFreeCallCount(), 0);
+
 // Test that buffers allocated with a free callback through our APIs are
 // released when a Worker owning it exits.
 
 const w = new Worker(`require(${JSON.stringify(binding)})`, { eval: true });
 
-assert.strictEqual(getFreeCallCount(), 0);
 w.on('exit', common.mustCall(() => {
   assert.strictEqual(getFreeCallCount(), 1);
 }));