test: fix flaky test-async-wrap-uncaughtexception

It's possible for `beforeExit` to be emitted more than once if work is
scheduled by its listeners. Accommodate this fact in the test.

Fixes: nodejs#16210

test/parallel/test-async-wrap-uncaughtexception.js

@@ -33,7 +33,7 @@ hooks = async_hooks.createHook({
 }).enable();
 
 
-process.on('uncaughtException', common.mustCall(() => {
+process.once('uncaughtException', common.mustCall(() => {
   assert.strictEqual(call_id, async_hooks.executionAsyncId());
   call_log[2]++;
 }));