Update Dockerfile to fix mermaid copypasta error

Dockerfile

@@ -45,11 +45,7 @@ RUN apk add --no-cache git openssl py-pygments libc6-compat g++
 RUN wget https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_Linux-64bit.tar.gz -O - | tar -C /opt/appbin -xvzf - 
 
 ## Install Mermaid CLI (along with pupeeter and Chromium)
-RUN apk add --no-cache npm \
-  && cd /root \
-  && npm install mermaid.cli
-
-ENV PATH="${PATH}:/root/node_modules/.bin"
+RUN npm install mermaid.cli
 
 RUN export uid=1000 gid=1000 && \
     echo "appuser:x:${uid}:${gid}:AppUser,,,:/opt/course_builder:/bin/bash" >> /etc/passwd && \