Use YAML mapping in debian/upstream/metadata.
Fixed-Lintian-Issues:
 source: upstream-metadata-not-yaml-mapping
 source: upstream-metadata-not-yaml-mapping
 source: upstream-metadata-not-yaml-mapping
 source: upstream-metadata-not-yaml-mapping
 source: upstream-metadata-not-yaml-mapping
 source: upstream-metadata-not-yaml-mapping
