nextver should error when trying to generate a point release with a feature

[rockstar]

Recently, we tried to use changelog to generate a point release. At the time, v0.87.0 was the most recent release. We wanted to make a release the v0.83.x series, the result being v0.83.1. changelog nextver was returning v0.88.0 as the next version. Upon further investigation, it's because the cherry-picked change to v0.83.x was a feat change, so changelog was rightfully trying to say "This can't be a point release." However, it's still incorrect, because v0.88.0 would end up missing changes that were added between v0.83.0 and v0.87.0, so that release would be wrong.

DOD:

• When running changelog nextver for a point release, an error should be returned if a non-fix oriented change is detected.