Flatpak: Add the talk-name flag for org.freedesktop.Screensaver

This brings the functionality in line with the old Flatpak release. This allows PCSX2 to inhibit the screensaver or screen blanking without needing to touch the mouse/keyboard while the VM is running.

.github/workflows/scripts/linux/flatpak/net.pcsx2.PCSX2.json

@@ -22,7 +22,8 @@
     "--socket=fallback-x11",
     "--socket=wayland",
     "--socket=pulseaudio",
-    "--filesystem=host:ro"
+    "--filesystem=host:ro",
+    "--talk-name=org.freedesktop.ScreenSaver"
   ],
   "modules": [
     "modules/10-libpcap.json",