ayab-shield: Make the top pour GND instead of +5V

[vthunder]

There’s been at least one instance on someone accidentally bridging IC pins to +5V because the top pour is +5V and the lines are thick and close to the pins. The idea here is to add some space and make the top GND to reduce this likelihood.

@VIPQualityPost please correct if I’ve misstated anything here

[VIPQualityPost]

nope, spot on. Do you want to fix it?

[VIPQualityPost]

This is fixed in #48 .