Rails - Advanced Forms and Active Record: Update wording and section numbers indicated in the assignment

[bellitabellota]

Because

The section numbers in bullet point 3 and 4 of "Querying basics" did partially not match with the ones in the Rails Guide.

Bullet point 2 of "Advanced querying" raised doubts about whether the correct section number is indicated.

This PR

• Section numbers and wording in bullet point 3 and 4 in "Querying basics" of the assignment instruction were updated
• The wording of bullet point 2 in "Advanced querying" was slightly modified to signal clearly that section 19 is the one TOP students should read.

Issue

Closes #29073

Pull Request Requirements

• [x ] I have thoroughly read and understand The Odin Project curriculum contributing guide
• [ x] The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• [x ] The Because section summarizes the reason for this PR
• [ x] The This PR section has a bullet point list describing the changes in this PR
• [ x] If this PR addresses an open issue, it is linked in the Issue section
• [ x] If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• [ x] If any lesson files are included in this PR, they follow the Layout Style Guide

[JoshDevHub]

Thank you for doing this 🚀