Fix: Fix text errors #3221 (#8708)

### What problem does this PR solve?

Fix: Fix text errors #3221

### Type of change

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

web/src/pages/agent/form/begin-form/begin-dynamic-options.tsx

@@ -50,7 +50,7 @@ export function BeginDynamicOptions() {
         );
       })}
       <BlockButton onClick={() => append({ value: '' })} type="button">
-        {t('flow.addVariable')}
+        {t('flow.addField')}
       </BlockButton>
     </div>
   );