fix: fp16 check python version

Author: kaeun97

numba_cuda/numba/cuda/fp16.py

@@ -1,6 +1,6 @@
 # SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: BSD-2-Clause
-
+import sys
 import numba.core.types as types
 from numba.cuda._internal.cuda_fp16 import (
     typing_registry,
@@ -190,9 +190,10 @@ def exp_ol(a):
     return _make_unary(a, hexp)
 
 
-@overload(math.exp2, target="cuda")
-def exp2_ol(a):
-    return _make_unary(a, hexp2)
+if sys.version_info >= (3, 11):
+    @overload(math.exp2, target="cuda")
+    def exp2_ol(a):
+        return _make_unary(a, hexp2)
 
 
 @overload(math.tanh, target="cuda")