Chore: Drop unnecessary type: ignore in Snowflake Iceberg alter test

mypy does not require the assignment ignore on the patched columns lambda.

Signed-off-by: Guillem G <guillem.gimenez@titanos.tv>

Author: sineline

tests/core/engine_adapter/test_snowflake.py

@@ -1032,7 +1032,7 @@ def test_alter_table_iceberg(mocker: MockerFixture, make_mocked_engine_adapter:
 
     current_table = {"a": "INT"}
     target_table = {"a": "INT", "b": "INT"}
-    adapter.columns = lambda table_name, **kwargs: {  # type: ignore[assignment]
+    adapter.columns = lambda table_name, **kwargs: {
         k: exp.DataType.build(v)
         for k, v in (current_table if table_name == "test_table" else target_table).items()
     }