fix[test]: fix a boundary case in decimal fuzzing (#3918)

change to not test the boundary condition at all, but rely on whether
`ExprVisitor().visit()` throws an exception or not.

tests/unit/ast/nodes/test_fold_binop_decimal.py

@@ -39,7 +39,10 @@ def foo(a: decimal, b: decimal) -> decimal:
     try:
         vyper_ast = parse_and_fold(f"{left} {op} {right}")
         expr = vyper_ast.body[0].value
+
+        # check invalid values
         ExprVisitor().visit(expr, DecimalT())
+
         new_node = expr.get_folded_value()
         is_valid = True
     except (OverflowException, ZeroDivisionException):
@@ -81,11 +84,13 @@ def foo({input_value}) -> decimal:
     try:
         vyper_ast = parse_and_fold(literal_op)
         expr = vyper_ast.body[0].value
+
+        # check invalid intermediate values
         ExprVisitor().visit(expr, DecimalT())
+
         new_node = expr.get_folded_value()
         expected = new_node.value
-        lo, hi = DecimalT().decimal_bounds
-        is_valid = lo <= expected < hi
+        is_valid = True
     except (OverflowException, ZeroDivisionException):
         # for overflow or division/modulus by 0, expect the contract call to revert
         is_valid = False