PKGBUILD:
Add C7E7849466FE2358343588377258734B41C31549 as additional recognized valid PGP
key, as heftig might not be able to prepare releases and package for a while.
config:
Consolidate with defaults for 5.13.4 based on previous config.
Update CONFIG_LSM to order landlock before lockdown and re-add bpf, as the
issue discussed in https://bugs.archlinux.org/task/71270 seems to have been a
user-error (using obsolete kernel parameters).