Fix code snippet at set-up-function page

[tttol]

Description of changes:

When setting up the Lambda function by referring to the “Set up a Function” page, the following error occurred while executing the npx ampx sandbox command.

[Sandbox] Detected file changes while previous deployment was in progress. Invoking 'sandbox' again
File written: amplify_outputs.json
Custom operation sayHello requires both an authorization rule and a handler reference
Caused By: Custom operation sayHello requires both an authorization rule and a handler reference

Resolution: Check your data schema definition for syntax and type errors.

[Sandbox] Watching for file changes...

Page URL: https://docs.amplify.aws/nextjs/build-a-backend/functions/set-up-function/

By adding.authorization(allow => [allow.guest()]) to data/resource.ts, the error was resolved.

  sayHello: a
    .query()
    .arguments({
      name: a.string(),
    })
    .returns(a.string())
    .authorization(allow => [allow.guest()] // Add this line
    .handler(a.handler.function(sayHello)),

I think that the code snippet in the documentation needed some revisions, so I created a this PR. If there are any issues with my implementation process and it’s possible to resolve the problem without the line .authorization(allow => [allow.guest()]), could you suggest an alternative solution? I might be saying something incorrect because I’m new to AWS Amplify.

Related GitHub issue #, if available:

Instructions

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Which product(s) are affected by this PR (if applicable)?

• [ ] amplify-cli
• [ ] amplify-ui
• [ ] amplify-studio
• [ ] amplify-hosting
• [ ] amplify-libraries

Which platform(s) are affected by this PR (if applicable)?

• [ ] JS
• [ ] Swift
• [ ] Android
• [ ] Flutter
• [ ] React Native

Please add the product(s)/platform(s) affected to the PR title

Checks

• [x] Does this PR conform to the styleguide?

• [ ] Does this PR include filetypes other than markdown or images? Please add or update unit tests accordingly.

• [ ] Are any files being deleted with this PR? If so, have the needed redirects been created?

• [ ] Are all links in MDX files using the MDX link syntax rather than HTML link syntax?
  ref: MDX: [link](https://docs.amplify.aws/) HTML: <a href="https://docs.amplify.aws/">link</a>

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