chore: Remove redundant `mkdir`

- If local folder ownership is for example `644` it will fail to handle the `COPY` regardless (while `744` would work).
- Creating the directory with higher permissions in the container does not appear to help.

Dockerfile

@@ -6,8 +6,7 @@ RUN apk update && \
     rm -rf /var/cache/apk/* && \
     addgroup testssl && \
     adduser -G testssl -g "testssl user" -s /bin/bash -D testssl && \
-    ln -s /home/testssl/testssl.sh /usr/local/bin/ && \
-    mkdir -m 755 -p /home/testssl/etc /home/testssl/bin
+    ln -s /home/testssl/testssl.sh /usr/local/bin/
 
 USER testssl
 WORKDIR /home/testssl/