Update workaround for Ubuntu 24.04

Dockerfile

@@ -167,9 +167,9 @@ RUN    addgroup --quiet --gid 121 gap \
 
 #ENV LD_LIBRARY_PATH /usr/local/lib:${LD_LIBRARY_PATH}
 
-# use bash instead of dash for sh
-# /usr/lib/git-core/git-subtree uses sh and fails with "Maximum function recursion depth (1000) reached" for large projects when using dash
-RUN echo "dash dash/sh boolean false" | debconf-set-selections && DEBIAN_FRONTEND=noninteractive dpkg-reconfigure dash
+# /usr/lib/git-core/git-subtree: use bash instead of sh (= dash)
+# /usr/lib/git-core/git-subtree fails with "Maximum function recursion depth (1000) reached" for large projects when using dash in Debian/Ubuntu
+RUN sed 's|#!/bin/sh|#!/bin/bash|' -i /usr/lib/git-core/git-subtree
 
 # Set up new user and home directory in environment.
 USER gap