Both Paths: Recursion: Link to internal recursion exercises

[JoshDevHub]

Because

There were issues with offloading this to external resources with inaccurate solutions and funky problems. We decided to move the content in house. We now have the recursion exercises ready to go in both paths, so we can direct learners to them.

This PR

• Change assignment in the Ruby course's recursive methods lesson to point to the new Ruby recursion exercises.
• Change assignment in JavaScript course's recursive methods lesson to point to the new recursion exercises for JS.

Issue

Closes #27265

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
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[JoshDevHub]

@mao-sz

Let me know if you think all the pieces on this are good to go. Hopefully I have everything together, but just to double check:

1. Merge Restructure: Group exercises by curriculum section javascript-exercises#597
2. Merge this PR
3. Announce new changes in discord

[mao-sz]

@JoshDevHub also merge #30480

The 3 together should be what's needed, then the combined announcement 👍

The git commands learners should need to get everything over, if they don't want to just delete then refork + clone, should be in the previous announcement with the CSS exercises restructure