Log Message:
Update beats to version 6.8.13.

Pkgsrc changes:
 * Update checksums.

Upstream changes:

=== Beats version 6.8.13
===== Added
*Filebeat*
- Add container image in Kubernetes metadata. 13356 12688

=== Beats version 6.8.12
==== Bugfixes
*Filebeat*
- Fix Filebeat OOMs on very long lines {issue}19500[19500], {pull}19552[19552]

=== Beats version 6.8.11
==== Bugfixes
*Metricbeat*
- Fix bug incorrect parsing of float numbers as integers in Couchbase
  module {issue}18949[18949] {pull}19055[19055]

=== Beats version 6.8.10
==== Bugfixes
*Affecting all Beats*
- Fix `add_cloud_metadata` to better support modifying sub-fields
  with other processors. {pull}13808[13808]

=== Beats version 6.8.9
==== Bugfixes
*Heartbeat*
- Fix crashes when multiple TCP ports are specified. {pull}17262[17262]