Removed unused wk_col property of SpatialRefSys models.

Unused since ae7cb577ddbea48aaed26cbbf69c77078a99e221.

django/contrib/gis/db/backends/oracle/models.py

@@ -65,7 +65,3 @@ class OracleSpatialRefSys(models.Model, SpatialRefSysMixin):
     @property
     def wkt(self):
         return self.wktext
-
-    @classmethod
-    def wkt_col(cls):
-        return 'wktext'

django/contrib/gis/db/backends/postgis/models.py

@@ -67,7 +67,3 @@ class PostGISSpatialRefSys(models.Model, SpatialRefSysMixin):
     @property
     def wkt(self):
         return self.srtext
-
-    @classmethod
-    def wkt_col(cls):
-        return 'srtext'