Fix HTML comment formatting in index.html

[willum070]

The tag was breaking on staging, my guess is the missing space is the culprit.

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• samples/dds-datasets-polygon/index.html:19, tag maps_dds_datasets_polygon_attribution_div

You are about to delete 1 region tag.

• samples/dds-datasets-polygon/index.html:19, tag maps_dds_datasets_polygon_attribution_div

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