Ruby: Object Oriented Programming: Update reference to section

[ruben-vl]

The section that is referred to was renamed, but the reference itself was not. (https://github.com/TheOdinProject/curriculum/commit/565217133b4ec0b67724d6d3126f9c41ca4ac4b2#diff-ee41d717b540478bb5bb2df6d3c0e47e26957f9e20173e81810b62c90d896d97R12)

Because

The section title doesn't match any section title in the page anymore. It also refers to 'questions', which were not part of the 'Learning Outcomes' section from before, but are part of the current 'Knowledge check' section.

This PR

• Fixes the title of the section being referred to.

Issue

Additional Information

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• [X] I have thoroughly read and understand The Odin Project curriculum contributing guide
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• [X] If this PR addresses an open issue, it is linked in the Issue section
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