`AnnotatedElementUtils.getAllAnnotationAttributes(…)` missing `@Nullable`

[mp911de]

AnnotatedElementUtils.getAllAnnotationAttributes(…) is documented as

* @return a {@link MultiValueMap} keyed by attribute name, containing the annotation
* attributes from all annotations found, or {@code null} if not found

but the return type isn't annotated with @Nullable.

[sbrannen]

Good catch, @mp911de. 👍

This is a regression that was inadvertently introduced in 7.0 M1.

• Specify generic type nullness #34140