Ignore ruby32 by default (same as for lower ruby versions)

[chhtz]

This is required for Ubuntu 24.04 compatibility. Without this, one gets errors like

${SOME_PACKAGE} lists 'ruby' as dependency, but it is neither a normal package nor an osdeps package. osdeps reports: cannot resolve ruby: ruby is not an osdep and it cannot be resolved as a source package

Maybe there is a more future-proof way to fix this (i.e., not requiring to add an entry for every new version)

Somewhat related: orocos-toolchain/autoproj#38