Log Message:
Update RMagick to 2.9.0.

Changes:
RMagick 2.9.0
    o Fix #23209, improve RVG's letter spacing (patch from Jonah Fox)
    o Add Draw#kerning= attribute(available in ImageMagick 6.4.7-8)
    o Add Draw#interword_spacing= attribute (available in ImageMagick
      6.4.8-0)
    o Add Draw#kerning, Draw#interword_spacing primitive methods (available in
      ImageMagick 6.4.8-3)
    o Feature #23171, support ImageList, Draw, Pixel marshaling.
    o Support all the new EvaluateOperator constants