fix: remote python sdk namespace typing (#2620)

This changes the default values for some namespace parameters in the
remote python SDK from None to [], to match the underlying code it
calls.

Prior to this commit, failing to supply "namespace" with the remote SDK
would cause an error because the underlying code it dispatches to does
not consider None to be valid input.

python/python/tests/test_namespace.py

@@ -420,6 +420,10 @@ class TestNamespaceConnection:
         assert "table2" in table_names
         assert len(table_names) == 1
 
+        # Test that drop_table works without explicit namespace parameter
+        db.drop_table("table2")
+        assert len(list(db.table_names())) == 0
+
         # Should not be able to open dropped table
         with pytest.raises(RuntimeError):
             db.open_table("table1")
@@ -487,6 +491,11 @@ class TestNamespaceConnection:
         # Verify all tables are gone
         assert len(list(db.table_names())) == 0
 
+        # Test that table_names works with keyword-only namespace parameter
+        db.create_table("test_table", schema=schema)
+        result = list(db.table_names(namespace=[]))
+        assert "test_table" in result
+
     def test_table_operations(self):
         """Test various table operations through namespace."""
         db = lancedb.connect_namespace("temp", {"root": self.temp_dir})