Fix typo in index.rst #6257

Job	Run time
Build workflow from matrix	20s
Build and Verify Docs	7m 44s
Build MatX / Build MatX	3m 34s
Build RAPIDS / Check GH Event	2s
Build RAPIDS / rmm kvikio cudf cudf_kafka cuspatial	16m 44s
Build RAPIDS / rmm ucxx raft cuvs cumlprims_mg cuml	39m 45s
Build RAPIDS / rmm ucxx raft cugraph-ops cugraph cugraph-gnn	11m 39s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
Verify Dev Containers / Verify devcontainer files are up-to-date	18s
Verify and summarize workflow results	21s
Verify Dev Containers / ${{ matrix.devcontainer.name }}	0s
Build MatX / Notify Slack of MatX failure	0s
CI	1s
Build RAPIDS / Notify Slack of RAPIDS failure	0s
	1h 20m 28s

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