Add comma for expr delimiter to fix match arms

Add a comma as an expr delimiter, this will allow correct parsing of
match arm expressions.

gcc/rust/ChangeLog:

	* parse/rust-parse-impl.h (Parser::parse_expr): Add comma delimiter.

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

gcc/rust/parse/rust-parse-impl.h

@@ -12082,7 +12082,7 @@ Parser<ManagedTokenSource>::parse_expr (int right_binding_power,
     {
       TokenId id = current_token->get_id ();
       if (id == SEMICOLON || id == RIGHT_PAREN || id == RIGHT_CURLY
-	  || id == RIGHT_SQUARE)
+	  || id == RIGHT_SQUARE || id == COMMA)
 	return nullptr;
     }