Do not list the descendant branches for the tags in the YAML

Since we already list all the tag contained in each branch, including
the symmetrical list of descendant branches for each tag in the YAML is
wasting bytes with duplicated information.

We still use the list of descendant branches internally to compute which
tags are contained in each branch.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

bin/classes.py

@@ -143,6 +143,8 @@ class GitTag:
     @classmethod
     def to_yaml(cls, dumper, data):
         d = dataclasses.asdict(data)
+        # already represented by the list of tags on each branch
+        del d["descendant_branches"]
         return dumper.represent_dict(d)
 
     @staticmethod