Update SixLabors.ImageSharp.Drawing to 2.1.5

Upgraded the SixLabors.ImageSharp.Drawing package from version 2.1.4 to 2.1.5 in the Edi.Captcha.csproj file. This update may include bug fixes, performance improvements, or new features.

Author: EdiWang

src/Edi.Captcha/Edi.Captcha.csproj

@@ -16,7 +16,7 @@
     </PropertyGroup>
     <ItemGroup>
         <FrameworkReference Include="Microsoft.AspNetCore.App" />
-        <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.4" />
+        <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.1.5" />
     </ItemGroup>
     <ItemGroup>
         <None Include="..\..\README.md" Pack="true" PackagePath="\" />