Upgrade drawing library to the latest.

Author: andy840119

osu.Game.Rulesets.Karaoke/osu.Game.Rulesets.Karaoke.csproj

@@ -21,7 +21,7 @@
     <PackageReference Include="Lucene.Net" Version="4.8.0-beta00016" />
     <PackageReference Include="Lucene.Net.Analysis.Kuromoji" Version="4.8.0-beta00016" />
     <PackageReference Include="SixLabors.Fonts" Version="2.1.3" />
-    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.6" />
+    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.7" />
     <!--install because it might cause "Could not load file or assembly" error, might be removed eventually-->
     <PackageReference Include="System.Text.Encodings.Web" Version="9.0.2" />
     <PackageReference Include="WanaKanaSharp" Version="0.2.0" />