Log Message:
graphics/ruby-RMagick: update to 3.0.0

## RMagick 3.0.0

Breaking Changes:

- Drop support for Ruby < 2.3.
- Drop support for ImageMagick < 6.8.
- Raise error when `nil` or empty string are passed to `Image.read`. (#351)
- Monitor feature disabled on Windows. (#344)
- Note: ruby versions > 2.4 and ImageMagick versions > 6.8 are not *explicitly*
  supported, yet, but if you are using them already, they should continue to
  work in the same fashion.

Enhancements:

- Add feature `Image#channel_entropy` (#300)
- Many quality of life improvements in the codebase.

Bug Fixes:

- Many memory leaks fixed!
- Fix `LoadError` on Windows. (#315)
- fix argument count in `Image#morphology_channel` (#306)