x-gtk-file-dialog-help-text

x-gtk-file-dialog-help-text is a variable defined in `C source code'.
Its value is

t

Documentation:
If non-nil, the GTK file chooser will show additional help text.
If more space for files in the file chooser dialog is wanted, set this to nil
to turn the additional text off.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.