fix(curriculum): semantic/grammatical issue

[royjohnlee]

Checklist:

• I have read and followed the contribution guidelines.
• I have read and followed the how to open a pull request guide.
• My pull request targets the main branch of freeCodeCamp.
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Closes #55105

@Lebussy pointed out a grammatical mistake in the description in #55105, and @Dario-DC suggested a way to fix it.

From:
"Inside your getMode function, on the empty line above your return call forEach on array"

To:
Inside your getMode function, on the empty line above your return statement, call forEach on array.