Log Message:
Update logrotate to version 3.18.0.

Pkgsrc changes:
 * Remove patch integrated upstream.
 * Update checksums.

Upstream changes:

[3.18.0] - 2021-01-08
=====================
  - allow UIDs and GIDs to be specified numerically (#217)
  - add support for Zstandard compressed files (#355)
  - make `delaycompress` not to fail with `rotate 0` (#341)