Update README.md

Author: fsmosca

README.md

@@ -7,7 +7,7 @@ A Chess GUI based from Python using PySimpleGUI and Python-Chess modules. Users
 Windows exe file will be available upon release. In the meantime to get it running the following are required.
 * Python 3.7 and up
 * Python-chess v0.28.0 and up
-* PySimpleGUI
+* PySimpleGUI 4.0.0
 * Pyperclip
 
 ### Installation