nixos-render-docs: make manpage deflists a little nicer

indent the entire list by 4, just like each definition is already
indented by 4. this matches rendering in html, which indents terms once
and indents definitions twice.

pkgs/tools/nix/nixos-render-docs/src/nixos_render_docs/manpage.py

@@ -263,10 +263,10 @@ class ManpageRenderer(Renderer):
         return self._admonition_close()
     def dl_open(self, token: Token, tokens: Sequence[Token], i: int, options: OptionsDict,
                 env: MutableMapping[str, Any]) -> str:
-        return ""
+        return ".RS 4"
     def dl_close(self, token: Token, tokens: Sequence[Token], i: int, options: OptionsDict,
                  env: MutableMapping[str, Any]) -> str:
-        return ""
+        return ".RE"
     def dt_open(self, token: Token, tokens: Sequence[Token], i: int, options: OptionsDict,
                 env: MutableMapping[str, Any]) -> str:
         return ".PP"