update test sdk to release version

Author: tg123

ci.sh

@@ -6,4 +6,4 @@ set -e
 # Execute Unit tests
 cd tests
 dotnet restore
-dotnet xunit
+dotnet test

tests/tests.csproj

@@ -4,10 +4,10 @@
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0" />
-    <PackageReference Include="xunit" Version="2.3.0-beta4-build3742" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.0-beta4-build3742" />
-    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.0-beta4-build3742" /> 
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
+    <PackageReference Include="xunit" Version="2.3.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.0" />
+    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.0" />
   </ItemGroup>
   <ItemGroup>
     <None Include="assets/*" CopyToOutputDirectory="Always" />