Do not temporarily change U.pixelsize while creating object previews
in object_preview_render. It does nothing, but can affect UI drawing
since this is done in a thread.

The function that creates offscreen renders for object previews temporarily changes U.pixelsize to 2.0, creates the render, then sets it back to the previous value.

First, it is a bit odd to change this to a specific value that is not related to the current value. A user might have pixelsize set to 3.0 when this starts for accessibility issues. Best to use the current value.

Second it doesn't do anything. It would have visible effect if the render includes options like wireframe or cavity shaders. Those options do change with line width and we wouldn't want those features to become narrower than a pixel when these previews are resized and shown. But the renders do not include these features. Following compares the previews before and after this patch is applied:

Third these previews are done in a background thread. So if any UI drawing is done while rendering is occurring then it will draw fonts and widgets at the wrong size.