rstudio: use electron_34 (#397477)

  zip,

  git,

  makeWrapper,

  electron_33,

  electron_34,

  server ? false, # build server version

  pam,

  nixosTests,

let

  # Note: we shouldn't use the latest electron here, since the node-abi dependency might

  # need to be updated every time the latest electron gets a new abi version number

  electron = electron_33;

  electron = electron_34;

  mathJaxSrc = fetchzip {

    url = "https://s3.amazonaws.com/rstudio-buildtools/mathjax-27.zip";