process,worker: ensure code after exit() effectless

remove unused error

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: ywave620

test/parallel/test-worker-voluntarily-exit-followed-by-throw.js

@@ -16,8 +16,7 @@ if (isMainThread) {
   try {
     process.exit();
     throw new Error('xxx');
-    // eslint-disable-next-line no-unused-vars
-  } catch (err) {
+  } catch {
     workerData[0] = 1;
   }
 }