Draft: Allow read_code permission to search code w/ Zoekt

What does this MR do and why?

Users associated with a custrom role with the read_code permission should be able to search for results in code. This change fixes a defect that prevented users with the read_code permission from searching (via zoekt) through code that they should have access to.

#421024 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

1. Enable zoekt.
2. Create a custom role with :read_code enabled.
3. Invite a user to a group with the role created in the previous step.
4. Login as the new user.
5. Search for code at the group level.
6. Verify that search results are shown.