Remove deprecated colorbar behaviour

Duncan Macleodrequested to merge
github/fork/duncanmmacleod/clean-plot-colorbar-deprecation into main

This PR finalises two deprecations of the colorbar functionality:

  • remove the log keyword that has been deprecated for years
  • implement the change to the default fraction, now is 0.0 which means 'don't shrink the parent axes'

Merge request reports