Update connect to a Snap to match best practices

[Montoya]

Description

This updates the Connect to a Snap how-to page to match the latest best practices and clarify some of the steps.

Issue(s) fixed

Fixes #1275

Preview

Checklist

Complete this checklist before merging your PR:

• [ ] If this PR contains a major change to the documentation content, I have added an entry to the top of the "What's new?" page.
• [ ] The proposed changes have been reviewed and approved by a member of the documentation team.

[github-actions[bot]]

Preview published: snaps-connect-eip-6963

[github-actions[bot]]

Preview published: snaps-connect-eip-6963

[github-actions[bot]]

Preview published: snaps-connect-eip-6963

[github-actions[bot]]

Preview published: snaps-connect-eip-6963