[xaprepare] Don't try to copy files that no longer exist (#9941)

Context: b7e21ad

Commit b7e21ad moved `src/native/monodroid/` to
`src/native/mono/monodroid` in order to add a parallel tree for the
CoreCLR host.  However, the `xaprepare` code which used to copy
certain files from that directory wasn't updated, resulting in errors
on CI similar to:

	Step Xamarin.Android.Prepare.Step_CopyExtraResultFilesForCI failed: Could not find a part of the path '/Users/runner/work/1/s/src/native/monodroid'.
	System.InvalidOperationException: Step Xamarin.Android.Prepare.Step_CopyExtraResultFilesForCI failed: Could not find a part of the path '/Users/runner/work/1/s/src/native/monodroid'.
	  ---> System.IO.DirectoryNotFoundException: Could not find a part of the path '/Users/runner/work/1/s/src/native/monodroid'.

Fix the error by removing the offending line from `xaprepare`
completely, as we no longer have any `*.include.*` files there.
There used to be serialized mono config and library mapping files
here, but we no longer use them.

Author: grendello

build-tools/xaprepare/xaprepare/Steps/Step_CopyExtraResultFilesForCI.cs

@@ -69,8 +69,6 @@ void CopyExtraBuildFiles (string destinationRoot, Context context)
 				filesToCopyPreserveRelative.AddRange (Directory.GetFiles (javaInteropBuildConfigDir, "*.props"));
 			}
 
-			filesToCopyPreserveRelative.AddRange (Directory.GetFiles (Path.Combine (BuildPaths.XamarinAndroidSourceRoot, "src", "native", "monodroid"), "*.include.*"));
-
 			var buildConfigDir = Path.Combine (BuildPaths.XamarinAndroidSourceRoot, "bin", $"Build{context.Configuration}");
 			if (Directory.Exists (buildConfigDir)) {
 				foreach (var fileMatch in buildConfigFiles) {