Revert "mupdf: actually build and install the shared libraries version"

This reverts commit 3d4769a9e8.
This broke many packages; let's revert until that's resolved.
https://github.com/NixOS/nixpkgs/pull/237199#issuecomment-1607343333

pkgs/applications/misc/mupdf/default.nix

@@ -64,9 +64,11 @@ stdenv.mkDerivation rec {
     substituteInPlace Makerules --replace "(shell pkg-config" "(shell $PKG_CONFIG"
   '';
 
+  # Use shared libraries to decrease size
+  buildFlags = [ "shared" ];
+
   makeFlags = [
     "prefix=$(out)"
-    "shared=yes"
     "USE_SYSTEM_LIBS=yes"
     "PKG_CONFIG=${buildPackages.pkg-config}/bin/${buildPackages.pkg-config.targetPrefix}pkg-config"
   ] ++ lib.optionals (!enableX11) [ "HAVE_X11=no" ]