Remove Golang 1.20 from CI Testing

This merge request remove Golang 1.20 tool chain from CI testing as we remove support for this version of go(https://lists.torproject.org/pipermail/tor-project/2023-September/003688.html).

requested review from @cohosh

assigned to @shelikhoo

(@cohosh I have manually assigned you as everyone else are AFK today.)

approved this merge request

merged

mentioned in issue #40290