Fix dead link in "See Also" section

[solar138]

Fix link

What This PR Changes

• (Please explain here why you created the pull request and specify what it changes)
• Fix link in the https://docs.arduino.cc/learn/microcontrollers/digital-pins/ article so it actually redirects to https://docs.arduino.cc/language-reference/en/functions/digital-io/pinMode/ instead of a 404 page.

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[g-castronovo]

Weird because I can see both links working mmm