ipc: remove class key from view json
ipc: remove class key from view json

It turns out that i3 does not have a `class` key in the json description
of a view, but provides it through `window_properties.class`. Since
`window_properties` has been added by 8fc9328, we can remove `class`
altogether.

Signed-off-by: Franklin "Snaipe" Mathieu <f8c00d89ca94dbd2d6669e2b7d79cb352f4d9bbd@diacritic.io>

ascent12/sway,1ace/sway,1ace/sway,ascent12/sway,SirCmpwn/sway,ascent12/sway,1ace/sway