Change priority extra to priority optional.

Changes-By: lintian-brush
Fixes: lintian: priority-extra-is-replaced-by-priority-optional
See-also: https://lintian.debian.org/tags/priority-extra-is-replaced-by-priority-optional.html
8 jobs for kali/master in 6 minutes and 10 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #666956049
build

00:03:27

passed #666956050
build source

00:02:52

 
  Test
passed #666956055
autopkgtest

00:01:48

passed #666956054
lintian

00:01:04

passed #666956056
piuparts

00:02:24

passed #666956053
reprotest

00:02:42

passed #666956052
test-build-all

00:02:42

passed #666956051
test-build-any

00:01:35