Sorry, didn’t see that you were asking about per-SSID.
For that, you just enter the command under the SSID profile.
(Instant AP)(config)# wlan ssid-profile <ssid-profile>
(Instant AP) (SSID Profile <ssid-profile>)# deny-inter-user-bridging
(Instant AP) (SSID Profile <ssid-profile>)# end
(Instant AP)# commit apply