Flatpak: fix ladspa envvar

packaging/flatpak/org.kde.kdenlive-nightly.json

@@ -18,7 +18,7 @@
     "--env=TMPDIR=/var/tmp",
     "--env=QT_ENABLE_HIGHDPI_SCALING=1",
     "--env=FREI0R_PATH=/app/lib/frei0r-1",
-    "--env=LADSPA_PATH=/app/lib/ladspa"
+    "--env=LADSPA_PATH=/app/extensions/Plugins/ladspa:/app/lib/ladspa"
   ],
   "add-extensions": {
     "org.freedesktop.LinuxAudio.Plugins": {