Revert "Add .net6 support"

This reverts commit 4480020.

Author: FreePhoenix888

.github/workflows/CD.yml

@@ -19,7 +19,7 @@ jobs:
       with:
         submodules: true
     - name: Test
-      run: dotnet test -c Release -f net6
+      run: dotnet test -c Release -f net5
     - name: Generate PDF with CSharp code
       if: github.event_name == 'push'
       run: |

Platform.Threading.csproj

@@ -6,7 +6,7 @@
     <AssemblyTitle>Platform.Threading</AssemblyTitle>
     <VersionPrefix>0.1.1</VersionPrefix>
     <Authors>Konstantin Diachenko</Authors>
-    <TargetFrameworks>net472;netstandard2.0;netstandard2.1;net5;net6</TargetFrameworks>
+    <TargetFrameworks>net472;netstandard2.0;netstandard2.1;net5</TargetFrameworks>
     <AssemblyName>Platform.Threading</AssemblyName>
     <PackageId>Platform.Threading</PackageId>
     <PackageTags>LinksPlatform;Threading;ISynchronization;ISynchronizationExtensions;ISynchronized;ReaderWriterLockSynchronization;Unsynchronization;ConcurrentQueueExtensions;TaskExtensions;ThreadHelpers</PackageTags>

csharp/Platform.Threading.Tests/Platform.Threading.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net472;netcoreapp2.1;netcoreapp3.1;net5;net6</TargetFrameworks>
+    <TargetFrameworks>net472;netcoreapp2.1;netcoreapp3.1;net5</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>

csharp/Platform.Threading/Platform.Threading.csproj

@@ -6,7 +6,7 @@
     <AssemblyTitle>Platform.Threading</AssemblyTitle>
     <VersionPrefix>0.3.0</VersionPrefix>
     <Authors>Konstantin Diachenko</Authors>
-    <TargetFrameworks>net472;netstandard2.0;netstandard2.1;net5;net6</TargetFrameworks>
+    <TargetFrameworks>net472;netstandard2.0;netstandard2.1;net5</TargetFrameworks>
     <AssemblyName>Platform.Threading</AssemblyName>
     <PackageId>Platform.Threading</PackageId>
     <PackageTags>LinksPlatform;Threading;ISynchronization;ISynchronizationExtensions;ISynchronized;ReaderWriterLockSynchronization;Unsynchronization;ConcurrentQueueExtensions;TaskExtensions;ThreadHelpers</PackageTags>