chore(deps): update dependency microsoft.net.test.sdk to v18 (#2014)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Refit.GeneratorTests/Refit.GeneratorTests.csproj

@@ -21,7 +21,7 @@
   <ItemGroup>
     <PackageReference Include="System.Formats.Asn1" Version="9.0.*" />
     <PackageReference Include="coverlet.collector" Version="6.0.4" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
      <PackageReference Include="System.Text.RegularExpressions" Version="4.3.1" /> 
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.3" />

Refit.Tests/Refit.Tests.csproj

@@ -37,7 +37,7 @@
 
   <ItemGroup>
     <PackageReference Include="coverlet.msbuild" Version="6.0.4" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
     <PackageReference Include="System.Formats.Asn1" Version="9.0.3" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.3" />