Fix some unused imports to make checkstyle happy (#978)

jaxrs-api/src/main/java/jakarta/ws/rs/SeBootstrap.java

diff --git a/jaxrs-api/src/main/java/jakarta/ws/rs/SeBootstrap.java b/jaxrs-api/src/main/java/jakarta/ws/rs/SeBootstrap.java
index fa7a5cc..5cf9093 100644
--- a/jaxrs-api/src/main/java/jakarta/ws/rs/SeBootstrap.java
+++ b/jaxrs-api/src/main/java/jakarta/ws/rs/SeBootstrap.java
@@ -18,7 +18,6 @@
 
 import java.net.URI;
 import java.util.Optional;
-import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;