Remove dev feature flag from GET /users/search API

Issue Description

This API has been live on prod for a long time but the feature flag has not been removed.
Remove the dev FF from backend and all other repos where its being used.

Reason for adding dev FF

1. Add pagination when multiple filter is applied and user count greater than 100 - PR link

Usages in other repos

1. website-dashboard - Partial use 🟨
2. discord-slash-commands - None of the usages use FF 🟥

This is a subtask of #2075

Expected Behavior

Current Behavior

Screenshots

NA

Reproducibility

• This issue is reproducible
• This issue is not reproducible

Steps to Reproduce

NA

Severity/Priority

• Critical
• High
• Medium
• Low

Additional Information

Checklist

• I have read and followed the project's code of conduct.
• I have searched for similar issues before creating this one.
• I have provided all the necessary information to understand and reproduce the issue.
• I am willing to contribute to the resolution of this issue.

Start by searching the website-backend repository and the listed website-dashboard and discord-slash-commands repositories for the dev feature flag used by GET /users/search. Read PR #1607 to understand the pagination change, then confirm the dashboard's partial usage and the absence of relevant command usage. Done means the flag is removed from every actual usage without removing the live API behavior.