[bootstrap] Use http instead of https (faster and easier to maintain)

This MR introduces a "preventive" change to the way we boostrap our CI builds. Instead of using https, we use the http version of our proxy. The https version is subject to certificate maintenance and may stop working w/o notice, despite our efforts. The http version will impose less CPU requirements to the server and will be faster and maintenance-free.

changed the description

enabled an automatic merge when the pipeline for 6868a2cb succeeds

canceled the automatic merge

merged

mentioned in commit 37610647

mentioned in issue bob#269 (closed)