Update Dockerfile

1 job for master in 27 minutes and 36 seconds (queued for 2 seconds)
Name Stage Failure
image_build Build
2021-08-31 05:27:52 (50.3 MB/s) - ‘phantomjs-2.1.1-linux-x86_64.tar.bz2’ saved [23415665/23415665]

phantomjs has been installed to /home/rstudio/bin
ERROR: Invalid requirement: 'root:staff'
The command '/bin/sh -c R -f /tmp/install.R && R --quiet -e "install.packages('webshot'); webshot::install_phantomjs()" && pip3 install -r /tmp/requirements.txt $$ chown root:staff /usr/local/lib/R/site-library' returned a non-zero code: 1
Cleaning up file based variables
ERROR: Job failed: exit code 1