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_lint/src/early.rs

@@ -430,7 +430,7 @@ pub fn check_ast_node_inner<'a, T: EarlyLintPass>(
     // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
     for (id, lints) in cx.context.buffered.map {
         for early_lint in lints {
-            sess.delay_span_bug(
+            sess.span_delayed_bug(
                 early_lint.span,
                 format!(
                     "failed to process buffered lint here (dummy = {})",