Revert "validator: Add generic check_or."

This reverts commit cd93d0967f.

This check_or is redundant with check_union; it gives a misleading
error message for the non-matching case; and it has no type safety.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/lib/validator.py

@@ -582,15 +582,3 @@ def check_string_or_int(var_name: str, val: object) -> Union[str, int]:
         return val
 
     raise ValidationError(_("{var_name} is not a string or integer").format(var_name=var_name))
-
-
-def check_or(sub_validator1: Validator[Any], sub_validator2: Validator[Any]) -> Validator[Any]:
-    def f(var_name: str, val: object) -> Validator[Any]:
-        try:
-            return sub_validator1(var_name, val)
-        except ValidationError:
-            pass
-
-        return sub_validator2(var_name, val)
-
-    return f