x11-wm/mutter: Undo USE_LDCONFIG tweak
Revert "x11-wm/mutter: Tweak USE_LDCONFIG"
This reverts commit 4765ce804cca8dff967d20b33826d65943cf8591.
This is no longer needed after the gnome-shell NO_SHLIB_REQUIRES_GLOB
change.
Reported by: arrowd, tagattie