remove unreachable code paths from std.zig.Ast.lastToken
This function checks for various possibilities that are never produced
by the parser.
Given that lastToken is unsafe to call on an Ast with errors, I also
removed code paths that would be reachable on an Ast with errors.
ad38af77faTechatrix committed on 3/7/2025, 9:20:34 PMparent5765736