test: fix offending max-len linter error

Refer: #5935
PR-URL: #5980
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Phillip Johnsen <johphi@gmail.com>

test/known_issues/test-stdin-is-always-net.socket.js

@@ -11,7 +11,7 @@ if (process.argv[2] === 'child') {
   return;
 }
 
-const proc = spawn(process.execPath, [__filename, 'child'], { stdio: 'ignore' });
+const proc = spawn(process.execPath, [__filename, 'child'], {stdio: 'ignore'});
 // To double-check this test, set stdio to 'pipe' and uncomment the line below.
 // proc.stderr.pipe(process.stderr);
 proc.on('exit', common.mustCall(function(exitCode) {