Currently there is no option in Studio to only suppress forbidden term hits for AutoSuggest.

You could define a filter in your termbase (use MultiTerm Desktop or MultiTerm Administrator) and use it in the Trados project (at Home > Project Settings > Language Pairs > All Language Pairs > Termbases, column "Filter"). After doing this, the term will no longer appear in the term recognition or termbase search any more either.

This is not necessarily a problem, but:

while the filter is active the terminology verifier will not warn regarding the usage of forbidden terms during interactive translation or verification. So, to make this work one would have to disable the filter during verification.

Actually, filters work on entry level. So only complete entries can be filtered out. This means that the approach would only work if you have forbidden/"good" terms in separate entries.