Polyglossia: renaming figurname stopped working

[Akira Kakuto]

> This happened after the recent upgrade of the Debian packages to texlive
> 2018.20190227-2. Any suggestions?

Here it seems to work by the following change:
\begin{document}
\gappto\captionspolish{\renewcommand{\figurename}{Il.}}
--->
\gappto\captionspolish{\renewcommand{\figurename}{Il.}}
\begin{document}

that is, writing
\gappto\captionspolish{\renewcommand{\figurename}{Il.}}
in the preamble.

Best,
Akira