do not install ggplot2 suggests list

ggplot2 3.0 suggests sf, we do not want tidyverse to become rocker/geospatial quite yet

tidyverse/Dockerfile

@@ -14,7 +14,6 @@ RUN apt-get update -qq && apt-get -y --no-install-recommends install \
     --deps TRUE \
     tidyverse \
     dplyr \
-    ggplot2 \
     devtools \
     formatR \
     remotes \

tidyverse/devel/Dockerfile

@@ -13,7 +13,6 @@ RUN apt-get update -qq && apt-get -y --no-install-recommends install \
     --deps TRUE \
     tidyverse \
     dplyr \
-    ggplot2 \
     devtools \
     formatR \
     remotes \