Known Issues with 1.2.46

It looks like I updated the source code for a 1.2.46 release on 2023-06-29 but didn't actually fully release it.

1.2.x kept support for PROJ < 6.2, but that should be easily available everywhere now (2016-03-17) so it doesn't seem worth doing more work on this. Therefore I've added a tag (v1.2.46) and anyone wanting this can get it from git.