Update standards version to 4.7.4, no changes needed.

Upgrade checklist verified:
 4.3.0 → 4.4.0:
  * package uses debhelper
 4.4.0 → 4.4.1:
  * package has no Vcs-<type> fields
  * Files entries in debian/copyright don't refer to directories
 4.4.1 → 4.5.0:
  * Package does not create users
  * Package does not ship init files
 4.5.0 → 4.5.1:
  * Package does not have any patches
 4.5.1 → 4.6.0:
  * Package does not contain any references to lib64
 4.6.1 → 4.6.2:
  * Package does not provide x-window-manager alternative
 4.6.2 → 4.7.0:
  * Package does not use dpkg-divert
 4.7.0 → 4.7.1:
  * Package does not install to non-/usr paths
 4.7.3 → 4.7.4:
  * Package is not in non-free-firmware
Certainty: certain
Fixed-Lintian-Issues:
 source: ancient-standards-version 4.3.0 (released 2018-12-23) (current is *)
