data/campaigns: correct "... then" to "... than"

Inspired by seeing a spelling correction by Vultraz in the logs back in
February.

Cannot be backported to 1.11 yet due to the stringfreeze.
style.css: no margin-bottom for <pre>
wmllint: put off dryrun's verbosity check until after options are processed

Per discussion with Elvish Hunter on the forum. Having dryrun check for a
minimum verbosity level during the options for loop meant that -vd would
set the verbosity level to 1, while -dv would set it to 2.