Update syntax tree definition

compiler/rustc_ast/src/ast.rs

@@ -1616,7 +1616,7 @@ pub enum StrStyle {
     /// A raw string, like `r##"foo"##`.
     ///
     /// The value is the number of `#` symbols used.
-    Raw(u16),
+    Raw(u8),
 }
 
 /// An AST literal.