Fixed: Disable some flaky tests on MacOS

Co-Authored-By: ta264 <ta264@users.noreply.github.com>

src/NzbDrone.Common.Test/CacheTests/CachedFixture.cs

@@ -84,6 +84,7 @@ namespace NzbDrone.Common.Test.CacheTests
         }
 
         [Test]
+        [Platform(Exclude = "MacOsX")]
         public void should_honor_ttl()
         {
             int hitCount = 0;

src/NzbDrone.Common.Test/TPLTests/DebouncerFixture.cs

@@ -7,6 +7,7 @@ using NzbDrone.Common.TPL;
 namespace NzbDrone.Common.Test.TPLTests
 {
     [TestFixture]
+    [Platform(Exclude = "MacOsX")]
     public class DebouncerFixture
     {
         public class Counter

src/NzbDrone.Common.Test/TPLTests/RateLimitServiceFixture.cs

@@ -10,6 +10,7 @@ using FluentAssertions;
 namespace NzbDrone.Common.Test.TPLTests
 {
     [TestFixture]
+    [Platform(Exclude = "MacOsX")]
     public class RateLimitServiceFixture : TestBase<RateLimitService>
     {
         private DateTime _epoch;