fix: Use correct type for pyarrow.csv.read_csv

Resolves:
```py
File ../altair/.venv/Lib/site-packages/pyarrow/csv.pyx:1258, in pyarrow._csv.read_csv()
TypeError: Cannot convert dict to pyarrow._csv.ParseOptions
```

altair/datasets/_readimpl.py

@@ -294,7 +294,7 @@ def pa_any() -> Sequence[Read[pa.Table]]:
     return (
         read(csv.read_csv, is_csv),
         _pa_read_json_impl(),
-        read(csv.read_csv, is_tsv, parse_options={"delimiter": "\t"}),
+        read(csv.read_csv, is_tsv, parse_options=csv.ParseOptions(delimiter="\t")),  # pyright: ignore[reportCallIssue]
         read(feather.read_table, is_arrow),
         read(parquet.read_table, is_parquet),
     )

tests/test_datasets.py

@@ -517,6 +517,12 @@ def test_spatial(backend: _Backend, name: Dataset) -> None:
             load(name)
 
 
+@backends
+def test_tsv(backend: _Backend) -> None:
+    load = Loader.from_backend(backend)
+    is_frame_backend(load("unemployment", ".tsv"), backend)
+
+
 @datasets_all
 @datasets_debug
 def test_all_datasets(polars_loader: PolarsLoader, name: Dataset) -> None: