util/find-doc-nits: Modernise printem()
util/find-doc-nits: Modernise printem()

It wasn't up to date with the new variables used to track information
on what's documented, what's in the .num files and what's in the
"missing" files.

Fixes #12117

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12125)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl