d/librem5-ci: Switch to crimson

debian/librem5-ci.yml

+variables:
+  L5_DOCKER_IMAGE: pureos/pureos:crimson
+
 include:
  - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-definitions.yml'
- - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-byzantium-jobs.yml'
- - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-common-jobs.yml'
+ - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/pureos-packaging-ci.yml'
 
 stages:
  - package