Fix(XUI): Remove unrecognized user_resize attribute from sun_moon_trackball

Problem:
A warning "Failed to parse parameter 'user_resize.'" appeared in the logs during UI loading, originating from sun_moon_trackball.xml.

Cause:
The 'user_resize' attribute is not a recognized or utilized parameter for the 'sun_moon_trackball' widget type, as defined in the corresponding C++
(LLVirtualTrackball).

Solution:
Removed the extraneous 'user_resize="false"' line from the sun_moon_trackball.xml widget definition.

Result:
Eliminates the parsing warning from the logs upon viewer startup or UI reload.

Testing:
- Launch viewer.
- Check logs for the absence of the "Failed to parse parameter 'user_resize.'" warning.

indra/newview/skins/default/xui/en/widgets/sun_moon_trackball.xml

@@ -3,7 +3,6 @@
     name="virtualtrackball"
     width="150"
     height="150"
-    user_resize="false"     
     increment_angle_mouse="1.5f"
     increment_angle_btn="1.0f"    
     image_sphere="VirtualTrackball_Sphere"