doc: recommend test-doc instead of lint-md

The documentation style guide used to recommend checking changes in the
docs by running `make lint-md`. This leaves out some important checks
which are contained in the `test-doc` build target. This commit also
replaces `lint` by `lint-md` in the list of `test-doc`'s prerequisites.

PR-URL: https://github.com/nodejs/node/pull/35708


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>