Update default executor and disable attestations

[nicoalonsop]

Checklist

• [x] All new jobs, commands, executors, parameters have descriptions
• [x] Examples have been added for any significant new features
• [x] README has been updated, if necessary

Motivation, issues

Update default executor and disable attestations. Fixes: #330 #325 #300

Description

I have updated the default executor from ubuntu-2004 to ubuntu-2204 and disabled the attestations.

I evaluated to use --provenance=false instead of the environment variable but that is not compatible with the docker engine version that is installed on ubuntu-2004. Using the environment variable allows you to use any version of the docker engine since it will not take effect if you are using an incompatible version.

[nicoalonsop]

Hey @brentmmarks, if you have some time, please let me know if I can do something to move this forward. Thanks!