Gate ArrowStringArrayNumpySemantics cudf.pandas proxy behind version …

…check (#16401)

## Description
`ArrowStringArrayNumpySemantics` was newly added in 2.1:
https://github.com/pandas-dev/pandas/blob/2.1.x/pandas/core/arrays/string_arrow.py#L488,
so putting the proxy wrapper behind a version check for pandas 2.0.x
compat

```ipython
In [1]: %load_ext cudf.pandas

In [2]: import pandas as pd

In [3]: pd.__version__
Out[3]: '2.0.0'
```

## Checklist
- [ ] I am familiar with the [Contributing
Guidelines](https://github.com/rapidsai/cudf/blob/HEAD/CONTRIBUTING.md).
- [ ] New or existing tests cover these changes.
- [ ] The documentation is up to date with these changes.

python/cudf/cudf/pandas/_wrappers/pandas.py

@@ -26,6 +26,7 @@
 )
 
 import cudf
+import cudf.core._compat
 
 from ..annotation import nvtx
 from ..fast_slow_proxy import (
@@ -556,13 +557,14 @@ def Index__setattr__(self, name, value):
     },
 )
 
-ArrowStringArrayNumpySemantics = make_final_proxy_type(
-    "ArrowStringArrayNumpySemantics",
-    _Unusable,
-    pd.core.arrays.string_arrow.ArrowStringArrayNumpySemantics,
-    fast_to_slow=_Unusable(),
-    slow_to_fast=_Unusable(),
-)
+if cudf.core._compat.PANDAS_GE_210:
+    ArrowStringArrayNumpySemantics = make_final_proxy_type(
+        "ArrowStringArrayNumpySemantics",
+        _Unusable,
+        pd.core.arrays.string_arrow.ArrowStringArrayNumpySemantics,
+        fast_to_slow=_Unusable(),
+        slow_to_fast=_Unusable(),
+    )
 
 ArrowStringArray = make_final_proxy_type(
     "ArrowStringArray",