Tweak delayed bug mentions.

Now that we have both `delayed_bug` and `span_delayed_bug`, it makes
sense to use the generic term "delayed bug" more.

compiler/rustc_span/src/symbol.rs

@@ -655,6 +655,7 @@ symbols! {
         default_method_body_is_const,
         default_type_parameter_fallback,
         default_type_params,
+        delayed_bug_from_inside_query,
         deny,
         deprecated,
         deprecated_safe,
@@ -1579,7 +1580,6 @@ symbols! {
         slice_patterns,
         slicing_syntax,
         soft,
-        span_delayed_bug_from_inside_query,
         specialization,
         speed,
         spotlight,