Default ABI version doesn't match SIP ones

[troopa81]

PyQt-builder default abi versions doesn't match SIP ones 12 13

[philthompson10]

These have been updated but it doesn't actually matter if they are not set to the latest versions. If a project needs a specific minimum version then they should explicitly set it their pyproject.toml.

[philthompson10]

In fact the specification of any minor number is confusing, somewhat arbitrary and unnecessary. It should be left to SIP to decide on a default minor number - PyQt-builder only needs to provide a default major number (ie. 12 or 13).

[philthompson10]

See issue #28 for a better description and resolution of the problem.