docs: make repository config first entry in sidebar

[HonkingGoose]

Changes

• Move sidebar items around so the repository config is the first item in the list

Context

I guess most of Renovate's users use the Mend hosted app? If that's true, the repository config items should be first in the sidebar.

The goal is to make the most important thing for most users, the first thing they see.

This PR is somewhat related, as it's also trying to make sure users end up at the right place in the docs:

• docs: clarify self-hosted options use #26561

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[renovate-release]

🎉 This PR is included in version 37.128.1 🎉

The release is available on:

• GitHub release
• 37.128.1

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