LaTeX -> doc: set

I'm trying to convert some `.tex` to `.docx` with a lot of complex math and `pandoc-2.11.3.1` can't convert `\set{..}` and similar cases.

Usual error looks like:
```
[WARNING] Could not convert TeX math '\set{1, \dots, n}', rendering as TeX:
\set{1, \dots, n}
^
unexpected "{"
expecting "%", "\\label", "\\nonumber" or whitespace
```

Test case:
```
\documentclass{scrartcl}

\begin{document}

$\set{1, \dots, n}$

\end{document}
```