utils: ignore leading whitespace in sa description

utils: ignore leading whitespace in sa description

load_sa_descriptions is used to parse the 'describe' lines for SpamAssassin
rules for the SpamInfo in the quarantine view.

The regex for parsing is too strict, since config lines can contain
leading whitespace (e.g. due to indentation in an 'ifplugin' block)

checked Mail::SpamAssassin::Conf::Parser and they strip leading/trailing
whitespace as well.

tested on my local setup with a quarantined mail which hit KAM_DMARC_STATUS.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>