bump System.Text.Encodings.Web up to 6.0.0

Author: smdn

src/PackageProvidedAPI.targets

@@ -100,7 +100,12 @@ SPDX-License-Identifier: MIT
       $(TargetFramework.StartsWith('net4')) or
       $(TargetFramework.StartsWith('netstandard'))
     ">
-      <ItemGroup><PackageReference Update="System.Text.Encodings.Web" Version="5.0.1" /></ItemGroup>
+      <ItemGroup>
+        <PackageReference Update="System.Text.Encodings.Web" Version="6.0.0" />
+        <PackageReference Update="System.Text.Encodings.Web" Version="5.0.1"
+          Condition="$(TargetFramework.StartsWith('net45')) or '$(TargetFramework)' == 'net46' or $(TargetFramework.StartsWith('netstandard1'))"
+        />
+      </ItemGroup>
     </When>
     <Otherwise>
       <ItemGroup><PackageReference Remove="System.Text.Encodings.Web" /></ItemGroup>