removed 'rm -rf' after update/install to fix error in 'install tzdata'

.dockerfilelintrc

@@ -1,6 +1,8 @@
 ---
+# https://github.com/replicatedhq/dockerfilelint
 rules:
   apt-get-upgrade: off
   apt-get-update_require_install: off
   apt-get_recommends: off
+  apt-get_missing_rm: off
   sudo_usage: off

Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:22.04
 
-RUN apt-get -y update && apt-get -y upgrade && rm -rf /var/lib/apt/lists/*
+RUN apt-get -y update && apt-get -y upgrade
 # The following is necessary to avoid an interactive prompt when installing r-base
 RUN DEBIAN_FRONTEND=noninteractive TZ=Etc/UTC apt-get -y install tzdata
 # instructions here: https://www.rstudio.com/products/shiny/download-server/ubuntu/