Fix: Appy to Apply in Tutorial #696

What Does This PR Do?

Replaces all instances of appy with apply in the tutorial (spelling fix).

Merge Requirements Satisfied

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• Check rendered output to ensure formatting is correct for renderings of wikilinks, note refs, tables, and images. Dendron: Show Preview can be used in your workspace to confirm the page renders as expected. Sometimes, Dendron: Reload Index needs to be ran if certain wikilinks aren’t working as expected. (ignore this if contribution is made via the Edit this page on GitHub button from the published site)
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