[SPARK-46437][FOLLOWUP] Update configuration.md to use include_api_gen

[nchammas]

What changes were proposed in this pull request?

As part of #44630 I neglected to update some places that still use the following Liquid directive pattern:

{% for static_file in site.static_files %}
    {% if static_file.name == 'generated-agg-funcs-table.html' %}
        {% include_relative generated-agg-funcs-table.html %}
        {% break %}
    {% endif %}
{% endfor %}

This PR replaces all remaining instances of this pattern with the new include_api_gen Jekyll tag.

Why are the changes needed?

For consistency in how we build our docs.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Manually building and reviewing the configuration docs.

Was this patch authored or co-authored using generative AI tooling?

No.

[HyukjinKwon]

Merged to master.