Remove libkrb5* transitional packages from rkerberos

libkrb5-ruby* are part of ruby-krb5-auth in Debian main, and while rkerberos
is the successor to krb5-auth, claiming to replace the packages causes
conflicts as version numbers aren't equivalent.
Bump as-yet unreleased wheezy rkerberos to 0.1.3 to avoid stray files in gem