Fix linebreaks in summary

Author: jmsmkn

.github/workflows/ci.yml

@@ -134,4 +134,6 @@ jobs:
                   retry -t 5 -- /bin/bash -c 'aws ecr-public get-login-password --region us-east-1 | docker login --username AWS --password-stdin public.ecr.aws/diag-nijmegen/grand-challenge/web-test-base'
                   retry -t 5 -- make push_web_test_base
             - name: Create Summary
-              run: echo "## Container Tag\n\`$(make container_tag)\`\n" >> $GITHUB_STEP_SUMMARY
+              run: |
+                echo "## Container Tag" >> $GITHUB_STEP_SUMMARY
+                echo "\`$(make container_tag)\`" >> $GITHUB_STEP_SUMMARY