delete any pre-existing R binary before running setup-r (#2628)
delete any pre-existing R binary before running setup-r (#2628)

Signed-off-by: yl790 <506e136862ca6a2cd6209c2ab7376874a235e7c2@rstudio.com>
rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr