man-pages: Don't have a separate docdev output

I got:

$ nix-env -f . -iA manpages
$ man mmap
No manual entry for mmap

which is suboptimal for a package that "documents the Linux kernel and
C library interfaces that are employed by user-space programs"
(https://www.kernel.org/doc/man-pages/).

Changed files
-5
pkgs
data
documentation
man-pages
-5
pkgs/data/documentation/man-pages/default.nix
···
sha256 = "1vimj3va16plxmv46rw6nzw4m9l11hb7r1d217y1bjpd5q8nw8qz";
};
-
# keep developer docs separately (man2 and man3)
-
outputs = [ "out" "docdev" ];
makeFlags = [ "MANDIR=$(out)/share/man" ];
-
postFixup = ''
-
moveToOutput share/man/man2 "$docdev"
-
'';
meta = with stdenv.lib; {
description = "Linux development manual pages";