If I'm not mistaken hplip rpm comes from hp for its printers and imaging device.
You could either do a
yum --skip-broken update
and then locate hpijs rpm from hp site and install it later.
Or if you dont need hp printer driver, rpm remove hplip, yum update and then figure out how to put hplip back in.
It would probably break something so check if you need hplip.
Btw, i found hpijs at pkgs.org and hplip at hplipopensource.com. Looks like third party rpm as in not from CentOS repo.