Fix TGUI Dev Server on 514! (#71374)

## About The Pull Request
Makes the dev server actually work on 514 again by reverting a removal
in reloader.js!

#71161 didn't take into account that we still use 514 in their TGUI
edits. Pain.
## Why It's Good For The Game
TGUI dev server works again, this is a good thing, I think!
## Changelog
Not player facing!

tgui/packages/tgui-dev-server/reloader.js

@@ -66,6 +66,8 @@ export const findCacheRoot = async () => {
 
 const onCacheRootFound = (cacheRoot) => {
   logger.log(`found cache at '${cacheRoot}'`);
+  // Plant a dummy browser window file, we'll be using this to avoid world topic. For byond 514.
+  fs.closeSync(fs.openSync(cacheRoot + '/dummy', 'w'));
 };
 
 export const reloadByondCache = async (bundleDir) => {
@@ -96,7 +98,7 @@ export const reloadByondCache = async (bundleDir) => {
       './*.+(bundle|chunk|hot-update).*'
     );
     try {
-      // Plant a dummy browser window file, we'll be using this to avoid world topic
+      // Plant a dummy browser window file, we'll be using this to avoid world topic. For byond 515.
       fs.closeSync(fs.openSync(cacheDir + '/dummy', 'w'));
 
       for (let file of garbage) {