go-module: workaround MissingUnpackerDep QA false positive

go-module: workaround MissingUnpackerDep QA false positive

The go.sum behavior in this eclass triggers a false positive from
pkgcheck, specifically:
MissingUnpackerDep: version ...: missing BDEPEND="app-arch/unzip"

The eclass & package do NOT invoke any direct unpacking of the zipfiles,
and leave that entirely to Go's builtin code, making app-arch/unzip
completely unneeded.

Adding packages using the new eclass functionality will spam the above
MissingUnpackerDep warning, so workaround it for now, until pkgcheck/QA
can not give the false positive.

Reference: https://github.com/pkgcore/pkgcheck/issues/214
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>