Backport #27555 by @wolfogre
It should be OK to increase the default queue length since the default
type is "level".
IMO, the old default length (100) is a little too small. See
https://github.com/go-gitea/gitea/issues/27540#issuecomment-1754269491
IIRC, a larger length could lead to more memory usage only when the type
is "channel," but it's an obscure case. Otherwise, it's just a limit
(for "level" or "redis").
Co-authored-by: Jason Song <i@wolfogre.com>
