Update CI pipeline to include xz package update

Added the `conda update -c default xz` step to ensure the xz package is updated in the pipeline environment.

.gitlab-ci.yml

@@ -54,6 +54,7 @@ update-osx:
     - conda activate base
     - conda update -c default conda
     - conda update -c default conda-build
+    - conda update -c default xz
   rules:
     - when: manual
   allow_failure: true  # Avoid blocking the pipeline if not run