No longer attempt to install the Sublime Text editor during vagrant up (#432)

* No longer attempt to install the Sublime Text editor during `vagrant up`
Starting around 2021-Sep, the official published instructions for
installing Sublime Text on Ubuntu Linux no longer seem to work.  If
this continues for much longer, it would be a good idea if the
`vagrant up` scripts no longer attempted to install it.

* Remove remaining mentions of Sublime in directory vm-ubuntu-20.04

vm-ubuntu-20.04/user-bootstrap.sh

@@ -288,17 +288,6 @@ Exec=/usr/bin/wireshark
 Comment[en_US]=
 EOF
 
-cat > ${DESKTOP}/Sublime\ Text.desktop << EOF
-[Desktop Entry]
-Encoding=UTF-8
-Type=Application
-Name=Sublime Text
-Name[en_US]=Sublime Text
-Icon=sublime-text
-Exec=/opt/sublime_text/sublime_text
-Comment[en_US]=
-EOF
-
 sudo mkdir -p /home/p4/Desktop
 sudo mv /home/${USER}/Desktop/* /home/p4/Desktop
 sudo chown -R p4:p4 /home/p4/Desktop/