What I'd advise is to upgrade to point just before it breaks, then update the permission to use a different name, then upgraded to 2.2 avoiding the name clash. Once upgraded then edit the permission to grant the permission to the users who need that permission based on your now renamed custom permission. Then remove your custom permission.
I'd do it this way so that you don't loose data on which users had that permission in the first place. Or rename the permission at the start then upgrade.
For those saying "why not upgrade to 4" there are many good reasons why you may not/ can not, use Django 4 at the moment such as reliance on unsupported 3rd party libs or, more commonly, regressions and lack of LTS. It's quite common for companies/projects that need stability to only upgrade from LTS version to LTS version as they can't risk the regressions that often happen in between