Ignore brotli test on osx

(cherry picked from commit 2afe6af5a6dac26fe9d2c20e806a93b621e18bbf)

src/NzbDrone.Common.Test/Http/HttpClientFixture.cs

@@ -207,6 +207,7 @@ public void should_execute_get_using_gzip()
         }
 
         [Test]
+        [Platform(Exclude = "MacOsX", Reason = "Azure agent update prevents brotli on OSX")]
         public void should_execute_get_using_brotli()
         {
             var request = new HttpRequest($"https://{_httpBinHost}/brotli");