Fix wrong separator line width after drawing vec icon

Was visible in Dynamic Context Menu add-on.

source/blender/editors/interface/interface_widgets.c

@@ -2625,6 +2625,7 @@ static void ui_draw_separator(const rcti *rect,  uiWidgetColors *wcol)
 	
 	glEnable(GL_BLEND);
 	glColor4ubv(col);
+	glLineWidth(1.0f);
 	sdrawline(rect->xmin, y, rect->xmax, y);
 	glDisable(GL_BLEND);
 }