Add missing import.

Author: cpovirk

src/java.base/share/classes/java/time/temporal/WeekFields.java

@@ -66,6 +66,7 @@
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.dataflow.qual.Pure;
 import org.checkerframework.dataflow.qual.SideEffectFree;
+import org.checkerframework.framework.qual.AnnotatedFor;
 
 import static java.time.temporal.ChronoField.DAY_OF_MONTH;
 import static java.time.temporal.ChronoField.DAY_OF_WEEK;