fix: element stats API is only returning rage clicks

[pauldambra]

follow-up to #21097
see: https://posthoghelp.zendesk.com/agent/tickets/12054

that removed the only-add-token mechanism of URL construction which is needed for the heatmap to work

• we pass in a string https://my-api/stats/?include=a&include=b
• toolbar fetch - unless you tell it not to converts the query parameters to an object
• so we end up with { include: b } since objects can't have two identical keys and kea doesn't handle converting it to an array of values
• rageclicks is the second include so becomes the only type of event we put in the heatmap

[github-actions]

Size Change: +69 B (0%)

Total Size: 824 kB

ℹ️ View Unchanged

Filename	Size	Change
frontend/dist/toolbar.js	824 kB	+69 B (0%)

_{compressed-size-action}

[marandaneto]

codewise is fine but I don't know this part of the code at all so it is better if somebody else also looks at it.