remove net5.0 from target frameworks

Author: smdn

src/Smdn.Reflection.ReverseGenerating.ListApi.Core/Smdn.Reflection.ReverseGenerating.ListApi.Core.csproj

@@ -4,7 +4,7 @@ SPDX-License-Identifier: MIT
 -->
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net5.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net6.0;netcoreapp3.1</TargetFrameworks>
     <RootNamespace>Smdn.Reflection.ReverseGenerating.ListApi.Core</RootNamespace>
     <VersionPrefix>1.1.0</VersionPrefix>
     <VersionSuffix></VersionSuffix>