Remove SuppressWarnings from NoopLock.java (#27416)

* Remove SuppressWarnings from NoopLock.java

* Remove Nonnull annotations from original

sdks/java/core/src/main/java/org/apache/beam/sdk/util/NoopLock.java

@@ -21,21 +21,19 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
-import javax.annotation.Nonnull;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.NonNull;
 
 /**
  * A lock which can always be acquired. It should not be used when a proper lock is required, but it
  * is useful as a performance optimization when locking is not necessary but the code paths have to
  * be shared between the locking and the non-locking variant.
  */
-@SuppressWarnings({
-  "nullness" // TODO(https://github.com/apache/beam/issues/20497)
-})
 public class NoopLock implements Lock, Serializable {
 
-  private static NoopLock instance;
+  private static @MonotonicNonNull NoopLock instance;
 
-  public static NoopLock get() {
+  public static @NonNull NoopLock get() {
     if (instance == null) {
       instance = new NoopLock();
     }
@@ -56,14 +54,13 @@ public boolean tryLock() {
   }
 
   @Override
-  public boolean tryLock(long time, @Nonnull TimeUnit unit) {
+  public boolean tryLock(long time, TimeUnit unit) {
     return true;
   }
 
   @Override
   public void unlock() {}
 
-  @Nonnull
   @Override
   public Condition newCondition() {
     throw new UnsupportedOperationException("Not implemented");