message: fix(Docker): correct symbol name
diff: FROM eosio/builder
  ARG branch=master
  -ARG symbole=SYS
  +ARG symbol=SYS
  RUN git clone -b $branch https://github.com/EOSIO/eos.git --recursive \
  && cd eos && echo "$branch:$(git rev-parse HEAD)" > /etc/eosio-version \
  