Rename HandlerInner::delay_span_bug as HandlerInner::span_delayed_bug.

Because the corresponding `Level` is `DelayedBug` and `span_delayed_bug`
follows the pattern used everywhere else: `span_err`, `span_warning`,
etc.

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -242,7 +242,7 @@ impl<'tcx> Visitor<'tcx> for UnsafetyChecker<'_, 'tcx> {
                     let assigned_ty = place.ty(&self.body.local_decls, self.tcx).ty;
                     if assigned_ty.needs_drop(self.tcx, self.param_env) {
                         // This would be unsafe, but should be outright impossible since we reject such unions.
-                        self.tcx.sess.delay_span_bug(
+                        self.tcx.sess.span_delayed_bug(
                             self.source_info.span,
                             format!("union fields that need dropping should be impossible: {assigned_ty}")
                         );