Ensure error recovery does not misparse in the event of ambiguous syntax

> even though a `NamedArgument` is required inside `{}`, it is matched successfully as a post-fix expression, and thus, failing for expecting the `try` body afterwards.

_Originally posted by @OmarTawfik in https://github.com/NomicFoundation/slang/pull/853#discussion_r1501403364_
            