Update CI to use Emacs 29

The PPA hasn't updated, so we're resorting to snap.

I also shouldn't need the BMC LaTeX package any more, so let's get rid
of that too.

.github/workflows/Dockerfile

@@ -4,12 +4,6 @@ MAINTAINER TEC <[email protected]>
 ENV LANG=C.UTF-8
 ENV DEBIAN_FRONTEND=noninteractive
 
-RUN echo "\033[1;34mAdd Emacs PPA.\033[0m" &&\
-  apt-get update &&\
-  apt-get install -y apt-utils software-properties-common &&\
-  add-apt-repository -y ppa:kelleyk/emacs &&\
-  apt-get update
-
 RUN echo "\033[1;34mUpdate.\033[0m" &&\
   apt-get update &&\
 ## Modified version of https://github.com/thomasWeise/docker-texlive-full
@@ -31,14 +25,12 @@ RUN echo "\033[1;34mUpdate.\033[0m" &&\
   mkdir -p /usr/share/info &&\
   echo "\033[1;34mInstalling utilities.\033[0m" &&\
   apt-get install -y sudo git gcc sqlite sqlite3 wget ncurses-term ripgrep xclip &&\
-  echo "\033[1;34mInstalling Emacs\033[0m" &&\
-# Emacs 28 (no-X)
-  apt-get install -y emacs28-nox &&\
+  echo "\033[1;34mInstalling Emacs 29\033[0m" &&\
+  snap install emacs --classic --channel=29.2/stable &&\
   echo "\033[1;34mInstalling cairosvg and curl (for emojis).\033[0m" &&\
   apt-get install -y curl cairosvg &&\
   echo "\033[1;34mInstalling TeX Live packages.\033[0m" &&\
 # install TeX Live and ghostscript as well as other tools (inkscape for svg)
-  git clone https://github.com/tecosaur/BMC.git /usr/share/texmf/tex/latex/bmc &&\
   apt-get install -y texlive-base texlive-latex-recommended texlive-fonts-extra latexmk inkscape &&\
 # delete Tex Live sources and other potentially useless stuff
   echo "\033[1;34mDelete TeX Live sources and other useless stuff.\033[0m" &&\