change name of credits button from license to credits

main.go

@@ -754,7 +754,7 @@ func main() {
 		dialog.ShowInformation("about pi", fmt.Sprintf("the XMPP client from hell\n\npi is an experimental XMPP client\nwritten by Sunglocto in Go.\n\nVersion %s", version), w)
 	})
 
-	licensesbtn := fyne.NewMenuItem("license", func() {
+	licensesbtn := fyne.NewMenuItem("credits", func() {
 		CreditsWindow(fyne.CurrentApp(), fyne.NewSize(800, 400)).Show()
 	})