test: fix linting issues in fastutf8stream tests

- Add mandatory require('../common') as first import in both test files
- Fix trailing spaces issues
- All JavaScript linting now passes

Author: mcollina

test/parallel/test-fastutf8stream-flush-mocks.js

@@ -1,5 +1,6 @@
 'use strict';
 
+require('../common');
 const { test } = require('node:test');
 const tmpdir = require('../common/tmpdir');
 const {

test/parallel/test-fastutf8stream-sync.js

@@ -1,5 +1,6 @@
 'use strict';
 
+require('../common');
 const { test } = require('node:test');
 const tmpdir = require('../common/tmpdir');
 const {
@@ -177,7 +178,7 @@ test('Utf8Stream sync large data write', async (t) => {
       else resolve(stat);
     });
   });
-  
+
   strictEqual(stat_result.size, length);
 
 });
@@ -206,7 +207,7 @@ test('Utf8Stream sync with emoji', async (t) => {
       else resolve(stat);
     });
   });
-  
+
   strictEqual(stat_result.size, length);
   const char = Buffer.alloc(4);
   const readFd = openSync(dest, 'r');
@@ -270,7 +271,7 @@ test('Utf8Stream sync with multiple unicode writes', async (t) => {
   }
 
   ok(true, 'writes completed successfully');
-  
+
   await new Promise((resolve) => {
     readFile(dest, 'utf8', (err, data) => {
       t.assert.ifError(err);