Fix for ns timestamp non utc (#3142)

Closes #3127  

# Rationale for this change
`pa.timestamp("ns", tz="US/Pacific") converts to TimestampNanoType()`
(tz-naive) instead of raising `TypeError`. The `us` path correctly
rejects non-UTC timezones.

raises TypeError
`visit_pyarrow(pa.timestamp("us", tz="US/Pacific"),
_ConvertToIceberg())`

silently drops timezone
`visit_pyarrow(pa.timestamp("ns", tz="US/Pacific"),
_ConvertToIceberg(format_version=3))`

Fixes this by adding the correct elif clause
## Are these changes tested?
Yes - added a couple of tests in the pyarrow visitor

## Are there any user-facing changes?
It fixes the behavior that was a bug, so I think it would be.

Author: nssalian

pyiceberg/io/pyarrow.py

@@ -1451,7 +1451,7 @@ def primitive(self, primitive: pa.DataType) -> PrimitiveType:
                 elif self._format_version >= 3:
                     if primitive.tz in UTC_ALIASES:
                         return TimestamptzNanoType()
-                    else:
+                    elif primitive.tz is None:
                         return TimestampNanoType()
                 else:
                     raise TypeError(

tests/io/test_pyarrow_visitor.py

@@ -63,6 +63,7 @@
     NestedField,
     StringType,
     StructType,
+    TimestampNanoType,
     TimestampType,
     TimestamptzType,
     TimeType,
@@ -226,6 +227,18 @@ def test_pyarrow_timestamp_tz_invalid_tz() -> None:
         visit_pyarrow(pyarrow_type, _ConvertToIceberg())
 
 
+def test_pyarrow_timestamp_ns_tz_invalid_tz() -> None:
+    pyarrow_type = pa.timestamp(unit="ns", tz="US/Pacific")
+    with pytest.raises(TypeError, match=re.escape("Unsupported type: timestamp[ns, tz=US/Pacific]")):
+        visit_pyarrow(pyarrow_type, _ConvertToIceberg(format_version=3))
+
+
+def test_pyarrow_timestamp_ns_no_tz_accepted() -> None:
+    pyarrow_type = pa.timestamp(unit="ns")
+    converted = visit_pyarrow(pyarrow_type, _ConvertToIceberg(format_version=3))
+    assert converted == TimestampNanoType()
+
+
 @pytest.mark.parametrize("pyarrow_type", [pa.string(), pa.large_string(), pa.string_view()])
 def test_pyarrow_string_to_iceberg(pyarrow_type: pa.DataType) -> None:
     converted_iceberg_type = visit_pyarrow(pyarrow_type, _ConvertToIceberg())