Minor documentation fix in HashFunction::create_or_throw.
Minor documentation fix in HashFunction::create_or_throw.

Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,webmaster128/botan,webmaster128/botan,randombit/botan,webmaster128/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,webmaster128/botan