Update dockerfile

[SafaTinaztepe]

Lines 26-28 failed for me, my Docker couldn't parse the heredoc string.

(base) me@the-computer:sqiggly-line/project-name$ sudo docker build . -t stablediffusion
Sending build context to Docker daemon  4.096kB
Error response from daemon: dockerfile parse error line 28: unknown instruction: GIT

Suggesting this fix, which allowed me to build the container.