Remove Ponos from CE

Based on !2227 (merged)

TODO:

• Remove & update tests

arkindex/ponos/models.py

@@ -62,6 +62,9 @@ class Farm(models.Model):
     def __str__(self) -> str:
         return "Farm {}".format(self.name)
 
+    def is_available(self, user) -> bool:
+        return True
+
 
 class Agent(models.Model):
     """