Steps to Reproduce:
Open the homepage on mobile.
Actual Results:
No rounded corners
Expected Results:
2px rounded corners on the module previews
See this example screenshot from variant A vs B tests:
https://www.mediawiki.org/wiki/Growth/Personalized_first_day/Variant_testing#/media/File:Growth_team_Var_A_vs._B_result_slide_2_2020-04-03.png