Update version to v6.0.0-beta.0

Author: retiutut

OpenBCI_GUI/OpenBCI_GUI.pde

@@ -62,7 +62,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 //                       Global Variables & Instances
 //------------------------------------------------------------------------
 //Used to check GUI version in TopNav.pde and displayed on the splash screen on startup
-String localGUIVersionString = "v6.0.0";
+String localGUIVersionString = "v6.0.0-beta.0";
 String localGUIVersionDate = "September 2023";
 String guiLatestVersionGithubAPI = "https://api.github.com/repos/OpenBCI/OpenBCI_GUI/releases/latest";
 String guiLatestReleaseLocation = "https://github.com/OpenBCI/OpenBCI_GUI/releases/latest";