erlang: fix empty documentation chunks in OTP 26

Without this, chunks are present but empty. Later versions do not seem
to be affected.

issue introduced in 284bdce430562a8e7a271d03fcc122cc4d72d498

pkgs/development/interpreters/erlang/generic-builder.nix

···
     ];
 
     env = {
-      # only build shell/IDE docs and man pages
-      DOC_TARGETS = "chunks man";
+      # only build man pages and shell/IDE docs
+      DOC_TARGETS = "man chunks";
     };
 
     buildInputs =