makepanda: Remove old panda3d.desktop file

This belonged to the runtime, but was missed in #734

makepanda/panda3d.desktop

@@ -1,11 +0,0 @@
-[Desktop Entry]
-Name=Panda3D
-Comment=Runs 3-D games and interactive applets
-TryExec=panda3d
-Exec=panda3d %U
-StartupNotify=true
-NoDisplay=true
-Terminal=false
-Type=Application
-Categories=Game;3DGraphics;Viewer;
-MimeType=application/x-panda3d;