ci: Run README tests for all projects supporting it

Use the new `test-readmes` recipe to test all README.md based end-to-end
integrations in a single target.

Signed-off-by: David Runge <dvzrv@archlinux.org>

.gitlab-ci.yml

@@ -76,7 +76,7 @@ test-readmes:
     - if: $CI_PIPELINE_SOURCE == "merge_request_event"
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
   script:
-    - WORKDIR="$(pwd)" runuser -w WORKDIR -l testuser -c 'env && cd "$WORKDIR" && just install-rust-dev-tools && just test-readme nethsm-cli'
+    - WORKDIR="$(pwd)" runuser -w WORKDIR -l testuser -c 'env && cd "$WORKDIR" && just install-rust-dev-tools && just test-readmes'
   stage: test
   tags:
     - vm