Add explicit BuildRequires for python3-pip
This PR fixes a build failure on RHEL 9 because python3-pip
is not available during the build.
On RHEL 8 python3-pip
is a dependency of python3
itself, so is implicitly a BuildRequires
for all python packages. For RHEL >= 9 this is not the case any more, so packages using %py3_install_wheel
need to bring it in explicitly.