Wrong comment string when using Dockerfile in listing in LaTeX files

[NicolaiRuckel]

Describe the bug: When using a dockerfile in a LaTeX llisting, commentstring gets set to # %s while Vim still detects the filetype as being tex.

To Reproduce: Create the following document as main.tex:

\documentclass{article}

\usepackage{listings}
\usepackage{minted}

\usemintedstyle{borland}

\setminted{%
  autogobble,
  xleftmargin=20pt,
  linenos
}

\begin{document}

\begin{listing}[ht]
  \begin{minted}{dockerfile}
  FROM java:8
  ADD example-app-1.0.jar app.jar
  EXPOSE 8761
  ENTRYPOINT ["java", "-jar", "/app.jar"]
  \end{minted}
  \caption{Simple \texttt{Dockerfile} example.}
  \label{lst:example-docker}
\end{listing}
\end{document}

Running :verbose set commentstring gives the following output:

commentstring=# %s
      Last set from ~/dotfiles/config/nvim/plugged/vim-polyglot/syntax/dockerfile.vim line 42