[Leaflet] does not render intro and outro wikitext

Setup

• MW version: 1.35.0-rc.2 (also tested in MW 1.31.10)
• DB (MySQL etc.): 10.1.47-MariaDB-0ubuntu0.18.04.1
• PHP version: 7.2.24-0ubuntu0.18.04.7
• SMW version: 3.2.1 (also tested in 3.1.6)
• SRF version: 3.2.0 (also tested in 3.1.0)
• Browsers and versions (if applicable):

Issue

wikitext in intro and outro parameters does not get rendered

Steps to reproduce

https://sandbox.semantic-mediawiki.org/wiki/Issue/SRF/623

Expected result: The link to [[Main Page]] should be a link.

Observed result: The link to [[Main Page]] is displayed in wikitext and not rendered (as can be seen below in the regular ask query.