fix(frontend): old brain legacy (#2310)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

frontend/app/studio/[brainId]/BrainManagementTabs/components/SettingsTab/SettingsTab.tsx

@@ -59,16 +59,17 @@ export const SettingsTabContent = ({
               <div className={styles.general_information}>
                 <GeneralInformation hasEditRights={hasEditRights} />
               </div>
-              {brain?.integration_description?.allow_model_change && (
-                <div className={styles.model_information}>
-                  <ModelSelection
-                    accessibleModels={accessibleModels}
-                    hasEditRights={hasEditRights}
-                    brainId={brainId}
-                    handleSubmit={handleSubmit}
-                  />
-                </div>
-              )}
+              {brain?.integration_description?.allow_model_change ||
+                (brain?.brain_type === "doc" && (
+                  <div className={styles.model_information}>
+                    <ModelSelection
+                      accessibleModels={accessibleModels}
+                      hasEditRights={hasEditRights}
+                      brainId={brainId}
+                      handleSubmit={handleSubmit}
+                    />
+                  </div>
+                ))}
             </div>
             {hasEditRights && (
               <div className={styles.save_button}>