Revert "singular: fix build" (#389465)

pkgs/by-name/si/singular/package.nix

···
       -i '{}' ';'
   '';
 
-  # FIXME: ugly hack for https://github.com/NixOS/nixpkgs/pull/389009
-  preConfigure = ''
-    substituteInPlace build-aux/ltmain.sh \
-      --replace 'for search_ext in .la $std_shrext .so .a' 'for search_ext in $std_shrext .so .a'
-  '';
-
   hardeningDisable = lib.optional stdenv.hostPlatform.isi686 "stackprotector";
 
   doCheck = true; # very basic checks, does not test any libraries