doc: fix OPENSSL_VERSION_NUMBER length in the synopsis
doc: fix OPENSSL_VERSION_NUMBER length in the synopsis

The number has 8 digits (not 9). It is a single integer `0xMNN00PP0L`.

Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>
Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16106)

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