Added child combinators explanation

[rampichino]

Because

Fix the issue of the child combinator > used in the examples but still not covered in the section.

This PR

• Move the content of Not everything adds to specificity outside the note box and make it a subsection.
• Rephrase the first senteces below the new subsection.

Issue

Closes #30067

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• 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
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide

[mao-sz]

1. Putting back the backticks so the symbols are in code blocks. They should not be removed.
2. Slight tweak of wording since I realised the descendant combinator (empty space) has already been introduced, so the current wording might seem slightly odd.

Suggested change

	When comparing selectors, you may come across special symbols for the universal selector (*) as well as combinators (+, ~, >, and an empty space). We will cover these later in the curriculum, so there is no need to dive into them yet. The core concept is that these symbols do not inherently convey any additional specificity.
	When comparing selectors, you may come across special symbols for the universal selector (`*`) as well as combinators (`+`, `~`, `>`, and an empty space). The ones you have not yet seen, we will cover these later in the curriculum, so there is no need to dive into them yet. The core concept is that these symbols do not inherently convey any additional specificity.