aptitude-changelog-parser: disable verbose instead of Perl warnings

aptitude-changelog-parser calls changelog_parse() from Dpkg::Changelog::Parse, which enables verbose by default: $options{verbose} //= 1; (i.e. set to 1 only if not defined yet). Setting this option to 0 before the call allows one to disable the parse_error warnings from Dpkg::Changelog, which we do not want for aptitude-changelog-parser.