(maint) fix up integration test

Instead of removing an attribute, it appears we were leaving
a file with a hidden attribute set, that would make the build
fail until that file was dealt with. Ensure we don't leave the
file in a bad state by explicitly removing the attribute.

src/chocolatey.tests.integration/infrastructure/filesystem/DotNetFileSystemSpecs.cs

@@ -145,7 +145,7 @@ public override void Context()
             {
                 base.Context();
                 SourceFile = Path.Combine(DestinationPath, "attributes.txt");
-                File.SetAttributes(SourceFile, (FileSystem.get_file_info_for(SourceFile).Attributes | FileAttributes.Hidden));
+                File.SetAttributes(SourceFile, (FileSystem.get_file_info_for(SourceFile).Attributes & ~FileAttributes.Hidden));
             }
 
             public override void Because()
@@ -162,7 +162,7 @@ public void visible_file_should_now_be_hidden()
             public override void AfterObservations()
             {
                 base.AfterObservations();
-                File.SetAttributes(SourceFile, (FileSystem.get_file_info_for(SourceFile).Attributes | FileAttributes.Hidden));
+                File.SetAttributes(SourceFile, (FileSystem.get_file_info_for(SourceFile).Attributes & ~FileAttributes.Hidden));
             }
         }