Restore TeXLive 2023 Compatability

This fix restores TexLive 2023 compatability which broke within the patchcmd of L220 in beamerfontthemeJuelich.sty; see also #22 (closed).

Beamer introduced a change in commit 4bed882a; see https://github.com/josephwright/beamer/commit/4bed882a250335d7f89bb00393f4509d57246a5b#diff-d246a5773c7737139aec3198d0c326739370905c4bdcfc09c189c480f33d7e73.

I've included the new definition in our patch command and also took the opportunity to reduce the search string (second argument of patchcmd) to the minimal necessary one, to make it potentially more robust to future changes… Note that \usebeamertemplate*{frametitle continuation} has changed to \beamer@insertframetitlecontinuation.

I have not thoroughly tested the fix. It works for my setup, though. Please, someone test this next and also test if smallcaps for titles still work.