add v6.8 as h1

Author: x-eun

libs/labelbox/CHANGELOG.md

@@ -4,17 +4,17 @@
 * Provide support to cancel tasks ([#1957](https://github.com/Labelbox/labelbox-python/pull/1957))
 * Added support for AUDIO attachment type ([#1956](https://github.com/Labelbox/labelbox-python/pull/1956))
 
-Version 6.8.0 (2025-02-20)
-### Added Support for Source Ontology Names in Relationships
+# Version 6.8.0 (2025-02-20)
+## Added Support for Source Ontology Names in Relationships
 
 Added the ability to specify relationships using `source_ontology_name` instead of a concrete source annotation. This enhancement is particularly useful for PDF document annotations where you can create relationships referencing ontology classes directly.
 
 Key changes:
 - Added optional `source_ontology_name` field to `Relationship` class
 - Made `source` field optional
 - Added validation to ensure either `source` or `source_ontology_name` is provided, but not both
-### Added search by name for `get_catalog_slice`
-### Added `get_catalog_slices` to get all slices
+## Added search by name for `get_catalog_slice`
+## Added `get_catalog_slices` to get all slices
 
 # Version 6.7.0 (2025-02-06)
 ## Added