fix deprecated coverage setting:

https://docs.gitlab.com/ee/ci/pipelines/settings.html#add-test-coverage-results-using-project-settings-removed
https://github.com/xd009642/tarpaulin#gitlab-pipelines

.gitlab/CI/build.gitlab-ci.yml

@@ -59,6 +59,7 @@ coverage:
   extends: .release
   stage: build
   image: registry.gitlab.com/veloren/veloren-docker-ci/cache/tarpaulin:${CACHE_IMAGE_TAG}
+  coverage: '/^\d+.\d+% coverage/'
   tags: ["veloren/veloren", "check"]
   script:
     - ln -s /dockercache/target target