Replace PackageIcon with PackageIconUrl because it does not work fine, remove Antlr.png

Author: KvanTTT

runtime/CSharp/Antlr.png

@@ -19,7 +19,7 @@
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <PackageLicenseExpression>BSD-3-Clause</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/antlr/antlr4</PackageProjectUrl>
-    <PackageIcon>Antlr.png</PackageIcon>
+    <PackageIconUrl>https://raw.github.com/antlr/website-antlr4/master/images/icons/antlr.png</PackageIconUrl>
     <PackageReleaseNotes>https://github.com/antlr/antlr4/releases</PackageReleaseNotes>
     <PackageTags>antlr parsing grammar</PackageTags>
     <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
@@ -37,15 +37,8 @@
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
-    <OutputPath>lib\Debug</OutputPath>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <Optimize>true</Optimize>
-    <OutputPath>lib\Release</OutputPath>
   </PropertyGroup>
-  <ItemGroup>
-    <None Update="Antlr.png">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </None>
-  </ItemGroup>
 </Project>