Fix stale DSV4 indexer metadata names in the TopK v2 dispatch test

[mmangkad]

#38947 renamed PagedIndexerMetadata.c4_seq_lens to compressed_seq_lens and turned the derived c4_page_size property into an explicit compressed_page_size field. #33672 landed a new test built on a pre-rename base, so its hand-built metadata stub still sets the old names and forward_c4_indexer blows up on main.

AttributeError: 'PagedIndexerMetadata' object has no attribute 'compressed_seq_lens'. Did you mean: 'max_compressed_seq_len'?
ERROR: test_v2_raw_output_uses_sparse_prefill_buffer_with_capture (__main__.TestDSV4TopKDispatch)
Ran 10 tests in 1.887s
FAILED (errors=1)

After: Ran 10 tests in 0.017s / OK.

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CI States

Latest PR Test (Base): ❌ Run #34614847128
Latest PR Test (Extra): ❌ Run #34614847087
Latest PR Test (AMD ROCm 10): ❌ Run #34614847159

[mmangkad]

/rerun-test test/registered/unit/layers/test_dsv4_nonpaged_indexer.py

[github-actions]

Results for /rerun-test test/registered/unit/layers/test_dsv4_nonpaged_indexer.py:

🚀 ubuntu-latest (1 test): ✅ View workflow run

cd test/ && python3 registered/unit/layers/test_dsv4_nonpaged_indexer.py