bin/get-pick-list.sh: handle fixes tag with missing colon

Every so often, we forget to add the colon after "fixes". Trivially
tweak the script to catch it.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
(cherry picked from commit 209525aa)