Remove warning in dask-cudf docs (#14454)

Move `from_delayed` and `concat` to appropriate subsections.

- Closes #14299

Authors:
  - Lawrence Mitchell (https://github.com/wence-)
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Bradley Dice (https://github.com/bdice)
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #14454

docs/dask_cudf/source/api.rst

@@ -19,21 +19,14 @@ data reading facilities, followed by calling
    :members:
       from_cudf,
       from_dask_dataframe,
+      from_delayed,
       read_csv,
       read_json,
       read_orc,
       to_orc,
       read_text,
       read_parquet
 
-.. warning::
-
-   FIXME: where should the following live?
-
-   .. autofunction:: dask_cudf.concat
-
-   .. autofunction:: dask_cudf.from_delayed
-
 Grouping
 ========
 
@@ -77,3 +70,7 @@ identical. The full API is provided below.
    :members:
    :inherited-members:
    :show-inheritance:
+
+.. automodule:: dask_cudf
+   :members:
+      concat