docs(troubleshooting): remove unnecessary call (#4327)

Removed unused `rm -rf` call. This directory doesn't exist (and same for all root docker images).

docs/troubleshooting.md

@@ -231,8 +231,7 @@ RUN wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key
     && apt-get update \
     && apt-get install -y google-chrome-unstable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst ttf-freefont \
       --no-install-recommends \
-    && rm -rf /var/lib/apt/lists/* \
-    && rm -rf /src/*.deb
+    && rm -rf /var/lib/apt/lists/*
 
 # If running Docker >= 1.13.0 use docker run's --init arg to reap zombie processes, otherwise
 # uncomment the following lines to have `dumb-init` as PID 1