Update SpiroNet.Editor.Avalonia.csproj

[skip ci]

src/SpiroNet.Editor.Avalonia/SpiroNet.Editor.Avalonia.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard1.1;net45</TargetFrameworks>
+    <TargetFrameworks>netstandard1.3;net45</TargetFrameworks>
     <OutputType>Library</OutputType>
     <EnableDefaultCompileItems>False</EnableDefaultCompileItems>
     <GenerateAssemblyInfo>False</GenerateAssemblyInfo>