app-antivirus/clamav: remove static-libs useflag

app-antivirus/clamav: remove static-libs useflag

as per policy
https://projects.gentoo.org/qa/policy-guide/installed-files.html?highlight=static#pg0302
for more context read:
https://flameeyes.blog/2011/08/29/useless-flag-static-libs/
https://archives.gentoo.org/gentoo-dev/message/2dada80c2b9c85b0e83e6328428bf8ab

Package-Manager: Portage-2.3.99, Repoman-2.3.22
Signed-off-by: Alessandro Barbieri <lssndrbarbieri@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/15489
Signed-off-by: Thomas Raschbacher <lordvan@gentoo.org>