Auto merge of #101296 - compiler-errors:head-span-for-enclosing-scope, r=oli-obk

Use head span for `rustc_on_unimplemented`'s `enclosing_scope` attr

This may make #101281 slightly easier to understand

compiler/rustc_span/src/symbol.rs

@@ -662,7 +662,6 @@ symbols! {
         emit_struct,
         emit_struct_field,
         enable,
-        enclosing_scope,
         encode,
         end,
         env,
@@ -1065,6 +1064,7 @@ symbols! {
         panic_unwind,
         panicking,
         param_attrs,
+        parent_label,
         partial_cmp,
         partial_ord,
         passes,