Fix: duplicate knowledgebase name validation logic (#8199)

### What problem does this PR solve?

Change the condition from checking for >1 to >=1 when validating
duplicate knowledgebase names to properly catch all duplicates. This
ensures no two knowledgebases can have the same name for a tenant.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/kb_app.py

@@ -107,7 +107,7 @@ def update():
 
         if req["name"].lower() != kb.name.lower() \
                 and len(
-            KnowledgebaseService.query(name=req["name"], tenant_id=current_user.id, status=StatusEnum.VALID.value)) > 1:
+            KnowledgebaseService.query(name=req["name"], tenant_id=current_user.id, status=StatusEnum.VALID.value)) >= 1:
             return get_data_error_result(
                 message="Duplicated knowledgebase name.")