Adapt to expl3 case changing change

[moewew]

we no longer use \text_titlecase:n for sentence casing.

See https://github.com/latex3/latex3/pull/1247.

[josephwright]

Looks good to me

[moewew]

Seemed to work fine in my tests also with the updated kernel.

[moewew]

Urgh! So close... There is a failure in the test for https://github.com/plk/biblatex/issues/1234. Need to investigate.

[moewew]

Seems this is not primarily a biblatex issue @josephwright. Consider

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{etoolbox}

\begin{document}
\newrobustcmd*{\hello}{hello}
\newrobustcmd*{\helloA}{helloA}
\newrobustcmd*{\helloB}{helloB}
\newrobustcmd*{\helloC}{helloC}
\newrobustcmd*{\helloD}{helloD}
\DeclareCaseChangeEquivalent{\hello}{%
     \CaseSwitch
       {\helloA}
       {\helloB}
       {\helloC}
       {\helloD}}

\MakeLowercase{\hello}

\MakeUppercase{\hello}

\MakeTitlecase{\hello}
\end{document}

which gives me

helloC helloB helloC

with the updated kernel.

Overleaf with the old kernel (https://www.overleaf.com/read/xbmyvpvkzchp#aaeb2c) has

helloC helloB helloD

Is that intentional?