update appimage download url

Author: zoff99

OFFLINE_MESSAGES.md

@@ -3,7 +3,7 @@ Offline Messages
 To get offline messages for your TRIfA App, install ToxProxy on a Linux Box at home and leave it running 0:00-24:00.<br>
 ### Installation instructions [using Google FCM for Push Messages]:
 
-* install ToxProxy for Linux: [appimage_binary](https://github.com/zoff99/ToxProxy/releases/latest/download/ToxProxy_x86_64.AppImage)
+* install ToxProxy for Linux: [appimage_binary](https://github.com/zoff99/ToxProxy/releases/download/nightly/ToxProxy_x86_64.AppImage)
 * run ToxProxy for Linux (**it will only write data to the current directory and below**):
 ```
 dummy@dummy:/home/dummy$ ./ToxProxy_x86_64.AppImage