org.springframework.lang.Nullable is banned by the
bannedNullabilityImports checkstyle rule on this line; the embargoed
commit that introduced this file predates that rule's adoption here.
Switch to org.jspecify.annotations.Nullable to match the rest of the
codebase (already used correctly elsewhere in this same file).
Signed-off-by: Josh Cummings <[email protected]>