fix(ui): bump expandprompt timeout to 15s

Author: psychedelicious

invokeai/frontend/web/src/features/prompt/PromptExpansion/expand.ts

@@ -27,7 +27,7 @@ export const expandPrompt = async (arg: { dispatch: AppDispatch; getState: AppGe
       dependencies,
       options: {
         prepend: true,
-        timeout: 10000,
+        timeout: 15000,
       },
     });
     assert(output.type === 'string_output');