[reports] Wrong URL when adding experiments to reports on the production platform

Issue explanation:

When going to the experiments page and adding experiments to a report from there:

The pop-up asks if we wish to go to the report with a button View Report

When clicking on that button, we are then sent to the page https://www.beat-eu.org/platform/platform/reports/<username>/<report>/

• gives a 404 page not found
• we have one extra platform in it.

Expected behavior:

We should be sent to https://www.beat-eu.org/platform/reports/<username>/<report>/