2.x: Also allow @SchedulerSupport on constructors. (#5940)

Author: vanniktech

src/main/java/io/reactivex/annotations/SchedulerSupport.java

@@ -28,7 +28,7 @@
  */
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
-@Target({ElementType.METHOD, ElementType.TYPE})
+@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.TYPE})
 public @interface SchedulerSupport {
     /**
      * A special value indicating the operator/class doesn't use schedulers.