refactor: floating window uses same win options

We were passing in `style = "minimal"` to `nvim_open_win`, which sets a
lot of default window options. If we remove that, the style of the
floating window will match the other oil windows. Users can use
`float.override` to set `style = "minimal"` if they want the previous
behavior.

lua/oil/init.lua

@@ -284,7 +284,6 @@ M.open_float = function(dir)
     height = height,
     row = row,
     col = col,
-    style = "minimal",
     border = config.float.border,
     zindex = 45,
   }