Update 4-relay-shield-basics.md

[Salmanktk]

Pin designations for internal wiring were not correctly mentioned in the initialization comments.

What This PR Changes

• In the tutorial to use the Arduino 4 relay shield the comments explaining why the specific pins were used were incorrect, as they all pointed to pin 2 for internal wiring in the initialization section.

Contribution Guidelines

• I confirm that I have read the contribution guidelines and comply with them.

[CLAassistant]

All committers have signed the CLA.

[jhansson-ard]

Thank you @Salmanktk for your review! ⭐