test: Skip flaky TestActiveLockCount

Race condition between task scheduling and lock count assertion causes
intermittent failures on ARM runners.

Author: lilith

tests/Imazen.Common.Tests/AsyncLockProviderTests.cs

@@ -14,7 +14,7 @@ public class AsyncLockProviderTests
         /// Tests that locks are cleaned up promptly, even in the case of contention and exceptions
         /// </summary>
         /// <exception cref="Exception"></exception>
-        [Fact]
+        [Fact(Skip = "Flaky: race between task start and active lock count assertion")]
         public async void TestActiveLockCount()
         {
             var provider = new AsyncLockProvider();