Remove NotNull annotation

We mostly annotate methods with @nullable and @NotNull is implicit

Co-authored-by: Martin Junghanns <martin.junghanns@neotechnology.com>

Author: FlorentinD

core/src/main/java/org/neo4j/gds/core/utils/progress/EmptyTaskStore.java

@@ -45,7 +45,7 @@ public Stream<UserTask> query(JobId jobId) {
     }
 
     @Override
-    public @NotNull Stream<UserTask> query(String username) {
+    public Stream<UserTask> query(String username) {
         return Stream.empty();
     }