Revert "run_vim.sh: use explicit HOME in /tmp (#11)" (#16)

This reverts commit e1bc2a1.

This could be made working with the following, but then the vimrc from
the HOME gets not picked up probably etc, so there needs to be another
fix for the Neovim case:

    exec su -l vimtest -c "env HOME=/tmp/vimtestbed-home \
      sh -c 'cd /testplugin && /vim-build/bin/$BIN $ARGS'"

Fixes https://github.com/tweekmonster/vim-testbed/pull/11/files#r82528988.

Author: blueyed

scripts/run_vim.sh

@@ -21,5 +21,4 @@ done
 
 # Run as the vimtest user.  This is not really for security.  It is for running
 # Vim as a user that's unable to write to your volume.
-cd /testplugin || exit
-exec su -l vimtest -c "env HOME=/tmp/vimtestbed-home /vim-build/bin/$BIN $ARGS"
+exec su -l vimtest -c "cd /testplugin && /vim-build/bin/$BIN $ARGS"