Reverting changes in pull #336

As suggested, with that old commit the "Go to Release Notes" link is broken referencing to "https://github.com/loki-project/session-desktop/releases/tag/1.0.1" for example.

main.js

@@ -428,7 +428,7 @@ ipc.on('ready-for-updates', async () => {
 
 function openReleaseNotes() {
   shell.openExternal(
-    `https://github.com/loki-project/loki-messenger/releases/tag/${app.getVersion()}`
+    `https://github.com/loki-project/loki-messenger/releases/tag/v${app.getVersion()}`
   );
 }