chore(value): remove deprecated greatest and least methods

BREAKING CHANGE: `Value.greatest` and `Value.least` are removed. Use
`ibis.greatest` and `ibis.least`, instead.

Author: gforsyth

ibis/expr/types/generic.py

@@ -301,14 +301,6 @@ def coalesce(self, *args: Value) -> Value:
         """
         return ops.Coalesce((self, *args)).to_expr()
 
-    @deprecated(as_of="8.0.0", instead="use ibis.greatest(self, rest...) instead")
-    def greatest(self, *args: ir.Value) -> ir.Value:
-        return ops.Greatest((self, *args)).to_expr()
-
-    @deprecated(as_of="8.0.0", instead="use ibis.least(self, rest...) instead")
-    def least(self, *args: ir.Value) -> ir.Value:
-        return ops.Least((self, *args)).to_expr()
-
     def typeof(self) -> ir.StringValue:
         """Return the string name of the datatype of self.