workspacesView: Fix off-by-one error
The scroll adjustment's upper value corresponds to the number of workspaces, not to the last workspace index. We want the latter when mirroring the layout in RTL locales, so subtract 1.
The scroll adjustment's upper value corresponds to the number of workspaces, not to the last workspace index. We want the latter when mirroring the layout in RTL locales, so subtract 1.