schema: Add version to issue ID fields

Add the "version" field to "issues" ID description, since it's the
combination of both the "id" and the "version" field which identifies
the "issue" object uniquely.

kcidb_io/schema/v04_01.py

@@ -904,6 +904,6 @@ class Version(PreviousVersion):
         checkouts=dict(id=str),
         builds=dict(id=str),
         tests=dict(id=str),
-        issues=dict(id=str),
+        issues=dict(id=str, version=int),
         incidents=dict(id=str),
     )