Use unbreakable space while plotting version numbers

[ErdaradunGaztea]

If package name is too short, then some version numbers are split into two lines. It unacceptable and the breakable space has to be replaced with unbreakable one.

Example:

plot_dependencies("shiny", show_version = TRUE)

[ErdaradunGaztea]

On the other hand, it may be (and probably is) simply the issue of \n not removed from version column while scrapping package descriptions. Which is being worked on already.