LibVT: fix pixel size calculations in terminal_did_resize

The scrollbar width must be factored in, and one too many
m_line_spacing were being factored into the height.  These caused an
initial terminal opening in 80x25 to get resized right away and
shrunk down to 77x24.

Libraries/LibVT/TerminalWidget.cpp

@@ -611,8 +611,8 @@ void TerminalWidget::terminal_history_changed()
 
 void TerminalWidget::terminal_did_resize(u16 columns, u16 rows)
 {
- m_pixel_width = (frame_thickness() * 2) + (m_inset * 2) + (columns * font().glyph_width('x'));
- m_pixel_height = (frame_thickness() * 2) + (m_inset * 2) + (rows * (font().glyph_height() + m_line_spacing)) - m_line_spacing;
+ m_pixel_width = (frame_thickness() * 2) + (m_inset * 2) + (columns * font().glyph_width('x')) + m_scrollbar->width();
+ m_pixel_height = (frame_thickness() * 2) + (m_inset * 2) + (rows * (font().glyph_height() + m_line_spacing));
 
  if (m_automatic_size_policy) {
  set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);