model: kill Origin.type attribute

it was still here for bw-compat but should not be necessary any more.

swh/model/hypothesis_strategies.py

@@ -75,7 +75,6 @@ def timestamps_with_timezone():
 def origins():
     return builds(
         Origin,
-        type=sampled_from(['git', 'hg', 'svn', 'pypi', 'deb']),
         url=urls())
 
 

swh/model/model.py

@@ -194,12 +194,6 @@ class TimestampWithTimezone(BaseModel):
 class Origin(BaseModel):
     """Represents a software source: a VCS and an URL."""
     url = attr.ib(type=str)
-    type = attr.ib(type=Optional[str], default=None)
-
-    def to_dict(self):
-        r = super().to_dict()
-        r.pop('type', None)
-        return r
 
 
 @attr.s(frozen=True)