Importmap: Fix fenced code block languages and linting

[MaoShizhong]

Because

There were several linting issues that could be autofixed, and one code block that contained two different languages would've flagged errors if it wasn't split into the appropriate separate blocks.

This PR

• Splits a ruby code block into ruby and erb, which would be more appropriate
• Fixes fenced code block language names to be the lowercase full names as per the TOP006 lint rule
• Runs the autofixer to address remaining lint errors

Issue

Closes #XXXXX

Additional Information

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[rlmoser99]

Thank you for taking the time to update this lesson! 🚀