Fix import typo

I believe this was not supposed to be `javax.annotation` but
`edu.umd.cs.findbugs.annotations` as everywhere else.

Fixes scylladb#149.

Author: Bouncheck

core/src/main/java/com/datastax/oss/driver/internal/core/pool/ChannelPool.java

@@ -52,6 +52,7 @@
 import com.datastax.oss.driver.shaded.guava.common.annotations.VisibleForTesting;
 import com.datastax.oss.driver.shaded.guava.common.collect.Sets;
 import edu.umd.cs.findbugs.annotations.NonNull;
+import edu.umd.cs.findbugs.annotations.Nullable;
 import io.netty.util.concurrent.EventExecutor;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.GenericFutureListener;
@@ -65,7 +66,6 @@
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Consumer;
-import javax.annotation.Nullable;
 import net.jcip.annotations.ThreadSafe;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

core/src/test/java/com/datastax/dse/driver/internal/core/graph/GraphRequestHandlerTestHarness.java

@@ -34,9 +34,9 @@
 import com.datastax.oss.driver.internal.core.session.throttling.PassThroughRequestThrottler;
 import com.datastax.oss.driver.internal.core.tracker.NoopRequestTracker;
 import com.datastax.oss.protocol.internal.Frame;
+import edu.umd.cs.findbugs.annotations.Nullable;
 import io.netty.channel.EventLoop;
 import java.time.Duration;
-import javax.annotation.Nullable;
 import org.mockito.ArgumentMatchers;
 import org.mockito.Mock;