Upgrade Golang to 1.20.7

What does this MR do?

This MR updates the Golang version in .tool-versions from 1.20.5 to 1.20.7.

Why was this MR needed?

This change will help reduce the number of Golang versions we need to install and manage in GDK.

What's the best way to test this MR?

What are the relevant issue numbers?