CI: use /etc/localtime instead of /etc/timezone
/etc/timezone is a legacy debian specific file. Let's use localtime. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1038849
- Related: #40414
/etc/timezone is a legacy debian specific file. Let's use localtime. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1038849