32-bit hosts virtualbox EOL

[Javier Agustìn Fernàndez Arroyo]

"Please also use version 5.2 if you still need support for 32-bit hosts, as
this has been discontinued in 6.0. Version 5.2 will remain supported until
July 2020."

FYI

That means, ROS will still be usable as guest, but not as host