Change the default value of showsTagField to true

The default value of showsTagField in macOS's NSSavePanel is true.

Therefore, in order to follow the standard behavior and not break
backwards-compatibility, let's change the default value of
showsTagField to true.

Reference:
https://developer.apple.com/reference/appkit/nssavepanel/1525589-showstagfield?language=objc

lib/browser/api/dialog.js

@@ -182,7 +182,7 @@ module.exports = {
     }
 
     if (showsTagField == null) {
-      showsTagField = false
+      showsTagField = true
     }
 
     const wrappedCallback = typeof callback === 'function' ? function (success, result) {