docs: regenerate the vector-index snippets the page imports

Porting the upstream changes replaced snippets/indexing.mdx with a hand
copy from lancedb/docs, which dropped six exports the vector-index page
still imports (`mint validate` warns on each) and added
PyQuantizationCustomParams, which had no source here.

The quantization test region is ported from lancedb/docs and the module
is regenerated, so every export comes from a test again. The regenerated
PyQuantizationCustomParams matches the copy byte for byte. Also fixes
"convetion" and "entires" on the page.

docs/web-tests/py/test_indexing.py

@@ -336,6 +336,25 @@ def test_vector_index_binary(tmp_db):
     assert not df.empty
 
 
+def test_quantization_custom_params(tmp_db):
+    table = tmp_db.create_table(
+        "quantization-custom-params",
+        _make_vector_rows(256, 64),
+        mode="overwrite",
+    )
+
+    # --8<-- [start:quantization_custom_params]
+    table.create_index(
+        index_type="IVF_RQ",
+        num_bits=2,
+        max_iterations=100,
+        sample_rate=512,
+    )
+    # --8<-- [end:quantization_custom_params]
+
+    assert table.list_indices()
+
+
 def test_vector_index_check_status(tmp_db):
     table = tmp_db.create_table(
         "vector_index_check_status",