Fix issue when updating Buffersize

[0xfalafel]

$Host.UI.RawUI.BufferSize = New-Object Management.Automation.Host.Size ($width, $height)

Can fail with the following error message:

Exception setting "buffersize": "Cannot set the buffer size because the size specified is too large or too small.

By specifying some large static value, we avoid this issue.

I did also change the line for WindowSize to match the style of the line above.