Ever since neovim introduced the nvim_ui_pum_set_bounds() call, GUI clients
have gained the ability to inform neovim of the current bounds of an
external popup menu provided by ext_popupmenu.
Since external popup menus are allowed to be any size in pixels which may
or may not line up cleanly on the grid, nvim allows for fractional
coordinates to be reported. This also will mean that in the event of this,
we'll end up with a cmp.WindowStyle with a float value for width/height -
which is incompatible with vim.api.nvim_open_win() and will cause us to hit
errors with GUI clients using this API call.
So, fix this by simply rounding up the width/height.
a9c701fa7e