Single-blind option

The system demonstrations track requires a single-blind submission but it's not clear how to render this.

Changing `\usepackage[review]{acl}` to `\usepackage[]{acl}` removes line numbers and is not suitable for the version submitted to review.

[This solution](https://tex.stackexchange.com/questions/673528/show-authors-in-acl-template) (replacing `\maketitle` as described there) appears not to work with the current version of the style files.

Context: using LuaLaTeX and acl_lualatex.tex

Start by reproducing the submission with LuaLaTeX using acl_lualatex.tex and the current acl style-file options. Read acl_lualatex.tex, the handling of review mode, and the current title-rendering path; done means a single-blind system-demonstration submission renders appropriately while retaining review line numbers.

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