I don't have the content filtering feature shown in your screenshot and in fact looking at this documentation:
https://n38.meraki.com/THECB-Meraki-Net/n/ezZOJcM/manage/support?kb_article=4170
an "Advanced Security Edition" license is required to use it. I assume this might require the MX platform as well, which we do not have. We have the MS and MR platforms, but not the MX.
Maybe I wasn't clear enough in my post. I am looking to block this traffic with the Layer 3/Layer 7 functionality built into the "Firewall and Traffic Shaping" part of the Wireless management category in the portal. These are the categories that I have available:
not shown: 1 more category, "advertising"