Color management: get rid of original byte buffer partial update

It was only used by opengl render and in fact it needed just to
set DISPLAY_BUFFER_INVALID flag for the image buffer.

In theory it wouldn't make any change to opengl render speed
(because this change just moved rect_from_float from color
management code to image save code). And could not see any speed
changes on my laptop.

source/blender/compositor/operations/COM_ViewerOperation.cpp

@@ -171,7 +171,7 @@ void ViewerOperation::updateImage(rcti *rect)
 {
 	IMB_partial_display_buffer_update(this->m_ibuf, this->m_outputBuffer, NULL, getWidth(), 0, 0,
 	                                  this->m_viewSettings, this->m_displaySettings,
-	                                  rect->xmin, rect->ymin, rect->xmax, rect->ymax, false);
+	                                  rect->xmin, rect->ymin, rect->xmax, rect->ymax);
 
 	this->updateDraw();
 }