Fix missing escaped newline.

Author: rouilj

scripts/Docker/Dockerfile

@@ -200,7 +200,7 @@ LABEL "org.opencontainers.image.vendor"="Roundup Issue Tracker Team" \
       "org.opencontainers.image.description"="Roundup Issue Tracker with multi-backend support installed via $source" \
       "org.opencontainers.image.version"="2.2.0" \
       "org.opencontainers.image.authors"="[email protected]" \
-      "org.opencontainers.image.licenses"="MIT AND ZPL-2.0 AND Python-2.0"
+      "org.opencontainers.image.licenses"="MIT AND ZPL-2.0 AND Python-2.0" \
       "org.opencontainers.image.documentation"="https://www.roundup-tracker.org/docs/installation.html"