security/openvas: fix build on armv7

• fix a wrong formatting specifier
• mute a well-intended but irrelevant warning. It would be better to just kill -Werror altogether as per policy, but I'll leave this up to the maintainer
• remove a REINPLACE_CMD now that the same effect is achieved by patch

Approved by: portmgr (build fix blanket)
MFH: 2023Q4