Main docs page says "* NOTICE *" in title tag

[bdice]

The title tag on the main page (https://docs.rapids.ai/api/cugraph/stable/) is "* NOTICE *", related to the DGL deprecation. That announcement is currently very loud, both visually and semantically. The main page heading probably shouldn't be * NOTICE * but something like "cuGraph Documentation". We can probably use a block for the deprecation announcement, like the .. note block used in https://docs.rapids.ai/api/cudf/stable/cudf_polars/. @acostadon