Revert "sync: update OpenAI moderation to use new model"

This reverts commit 1b56bdc526.

OpenAI told us to switch to this model for moderation, but this model
clearly isn't ready for production use yet.

src/backend/src/modules/puterai/OpenAICompletionService.js

@@ -282,10 +282,9 @@ class OpenAICompletionService extends BaseService {
     async check_moderation (text) {
         // create moderation
         const results = await this.openai.moderations.create({
-            model: 'omni-moderation-latest',
             input: text,
         });
-        
+
         let flagged = false;
 
         for ( const result of results?.results ?? [] ) {