definitions: Fail on lintian error

Otherwise nobody will ever look at the results.

I'm pretty sure this was the default at some point but clearly isn't anymore:

https://source.puri.sm/Librem5/debs/gnss-share/-/jobs/358230

Fixing these early makes review for PureOS maintainers simpler on e.g. new packaegs. This will certainly create some fallout but if urgency is needed one can always override L5_LINTIAN_OPTS in the gitlab-ci yml file for the moment.