SonarCloud and use indexed accessor in Mutex.kt.

Signed-off-by: Kenneth J. Shackleton <[email protected]>

selekt-java/src/main/kotlin/com/bloomberg/selekt/pools/Mutex.kt

@@ -52,7 +52,7 @@ internal class Mutex {
     }
 
     fun unlock() {
-        isLockedUpdater.set(this, 0)
+        isLockedUpdater[this] = 0
         LockSupport.unpark(waiters.peek())
     }