cygwin doesn't install cleanly in dockerfile so remove it
cygwin doesn't install cleanly in dockerfile so remove it

- doesn't seem to be necessary for the Windows build

(cherry picked from commit 85d202de42aa5eb3ef2ae4be46535e7848a7d870)

JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio