Remove libfreetype.so from adoptopenjdk's derivation.

This caused some reverse dependencies of adoptopenjdk to depend on
adoptopenjdk's libfreetype, rather than the NixOS
libfreetype. For example: https://github.com/NixOS/nixpkgs/issues/57733

Now the derivation does not contain libfreetype.so . The JRE links to
nixpkg's freetype:

$ ldd /nix/store/9iyxm1nkn35xhjgri041r980z4p5ls5g-adoptopenjdk-hotspot-bin-11.0.2/lib/libfontmanager.so | grep -i freetype
	libfreetype.so => /nix/store/ycbkq39cngzx19j829qzgdnw3mx3z78g-freetype-2.9.1/lib/libfreetype.so (0x0000795e30702000)