Require read_code instead of download_code for search

What does this MR do and why?

Require read_code instead of download_code for search

read_code is meant to be the abilities that are currently allowed by having download_code except specifically not related to downloading code. Users that can download_code can also read_code.

Contributes to: #376180 (closed)

Changelog: other

How to set up and validate locally

1. Create a private project
2. Add a commit with a new file
3. Add a user to the project with reporter access
4. Search within the project for the file and see results exist
5. Search within the project for the commit and get redirected to the commit
6. Add a user to the project with guest access
7. Search within the project for the file and see no results
8. Search within the project for the commit and see no results

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #376180 (closed)