Text edits to manual paages

Text edits to manual paages

This commit updates the wording in following man pages:

* ddns-confgen.rst
* delv.rst
* dig.rst
* dnssec-dsfromkey.rst
* dnssec-importkey.rst
* dnssec-keyfromlabel.rst
* dnssec-keygen.rst
* dnssec-revoke.rst
* dnssec-settime.rst
* dnssec-signzone.rst
* dnssec-verify.rst
* dnstap-read.rst
* filter-aaaa.rst
* host.rst
* mdig.rst
* named-checkconf.rst
* named-checkzone.rst
* named-nzd2nzf.rst
* named.conf.rst
* named.rst
* nsec3hash.rst
* nsupdate.rst
* pkcs11-destroy.rst
* pkcs11-keygen.rst
* pkcs11-list.rst
* pkcs11-tokens.rst
* rndc-confgen.rst
* rndc.rst