Minor import cleanup (#324)

Author: kanatti

src/main/java/dev/failsafe/AsyncExecutionImpl.java

@@ -17,7 +17,6 @@
 
 import dev.failsafe.internal.util.Assert;
 import dev.failsafe.spi.*;
-import dev.failsafe.spi.*;
 
 import java.util.List;
 import java.util.concurrent.CompletableFuture;