Recognize new JSpecify package name

So that its `@Nullable` annotation is treated as a type-use annotation and formatted accordingly. See jspecify/jspecify#260.

Fixes #869

COPYBARA_INTEGRATE_REVIEW=#869 from PicnicSupermarket:improvement/support-new-jpecify-package-name 7a0dc20
PiperOrigin-RevId: 495701635

core/src/main/java/com/google/googlejavaformat/java/JavaInputAstVisitor.java

@@ -285,6 +285,7 @@ private static ImmutableSetMultimap<String, String> typeAnnotations() {
     ImmutableSetMultimap.Builder<String, String> result = ImmutableSetMultimap.builder();
     for (String annotation :
         ImmutableList.of(
+            "org.jspecify.annotations.Nullable",
             "org.jspecify.nullness.Nullable",
             "org.checkerframework.checker.nullness.qual.Nullable")) {
       String simpleName = annotation.substring(annotation.lastIndexOf('.') + 1);