util/find-doc-nits: ignore macros ending in _fnsig
util/find-doc-nits: ignore macros ending in _fnsig

These are helper macros alongside the IMPLEMENT_ and DECLARE_ macros.

Reviewed-by: Matt Caswell <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10394)

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