[ci] Don't run classic tests on the Windows build/test stage (#7860)

Quick and easy win: don't run Classic smoke tests on the
Windows Build/Test stage.  Saves ~22 minutes on CI.

Author: jpobst

build-tools/automation/yaml-templates/build-windows.yaml

@@ -114,14 +114,6 @@ stages:
 
     - template: install-apkdiff.yaml
 
-    - template: run-nunit-tests.yaml
-      parameters:
-        useDotNet: false
-        testRunTitle: Smoke MSBuild Tests - Windows Build Tree
-        testAssembly: $(System.DefaultWorkingDirectory)\bin\Test$(XA.Build.Configuration)\net472\Xamarin.Android.Build.Tests.dll
-        testResultsFile: TestResult-SmokeMSBuildTests-WinBuildTree-$(XA.Build.Configuration).xml
-        nunitConsoleExtraArgs: --where "cat == SmokeTests"
-
     - template: run-nunit-tests.yaml
       parameters:
         testRunTitle: Smoke MSBuild Tests - Windows Dotnet Build