contrib: libplacebo: remove hack on the .pc file

That hack was introduced in 4e599bd5.
This has been fixed a long time ago. We require meson 0.56 which contains the
fix.

contrib/src/libplacebo/rules.mak

@@ -47,8 +47,6 @@ endif
 	cd $< && rm -rf ./build
 	cd $< && $(HOSTVARS_MESON) $(MESON) $(PLACEBOCONF) build
 	cd $< && cd build && ninja install
-# Work-around messon issue https://github.com/mesonbuild/meson/issues/4091
-	sed -i.orig -e 's/Libs: \(.*\) -L$${libdir} -lplacebo/Libs: -L$${libdir} -lplacebo \1/g' $(PREFIX)/lib/pkgconfig/libplacebo.pc
 # Work-around for full paths to static libraries, which libtool does not like
 # See https://github.com/mesonbuild/meson/issues/5479
 	(cd $(UNPACK_DIR) && $(SRC_BUILT)/pkg-rewrite-absolute.py -i "$(PREFIX)/lib/pkgconfig/libplacebo.pc")