Move is_used_keyword_conditional.

So the order of the `Symbol::is_*` predicates match the order of the
keywords list.

Author: nnethercote

Diff for: compiler/rustc_span/src/symbol.rs

@@ -2673,14 +2673,14 @@ impl Symbol {
         self >= kw::As && self <= kw::While
     }
 
-    fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
-        (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
-    }
-
     fn is_unused_keyword_always(self) -> bool {
         self >= kw::Abstract && self <= kw::Yield
     }
 
+    fn is_used_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
+        (self >= kw::Async && self <= kw::Dyn) && edition() >= Edition::Edition2018
+    }
+
     fn is_unused_keyword_conditional(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
         self == kw::Gen && edition().at_least_rust_2024()
             || self == kw::Try && edition().at_least_rust_2018()