Fix friendly class to friendly struct qualification

gcc/rust/ChangeLog:

	* parse/rust-parse.h: Change class to struct for friend qualification.

Signed-off-by: Pierre-Emmanuel Patry <[email protected]>

Author: P-E-P

gcc/rust/parse/rust-parse.h

@@ -782,7 +782,7 @@ template <typename ManagedTokenSource> class Parser
 
   // don't want to make things *only* AttributeParser uses public
   // TODO: fold more of AttributeParser into Parser?
-  friend class ::Rust::AST::AttributeParser;
+  friend struct ::Rust::AST::AttributeParser;
 };
 
 std::string extract_module_path (const AST::AttrVec &inner_attrs,