danger: Make two commit guidelines warnings instead of errors

1. In some cases, it doesn't make sense to enforce a commit body when
   the changes changes many lines/files, but are very trivial (e.g. mass
   replacemnt/removal).
2. In some cases (e.g. when including stacktrace), it doesn't make sense
   to wrap lines, making it impossible to satisfy the "details line may
   not be longer than 72 characters".

Signed-off-by: Rémy Coutable <remy@rymai.me>