Change render octree balance default

Another bug in the octree has been discovered which can cause flickering in rare circumstances : #42895

For safety until this is fixed properly this PR reverts the default state of the octree to match the old behaviour, which doesn't appear exhibit the bug (or at least not as readily).

doc/classes/ProjectSettings.xml

@@ -1202,7 +1202,7 @@
 			See also [member rendering/quality/skinning/force_software_skinning].
 			[b]Note:[/b] When the software skinning fallback is triggered, custom vertex shaders will behave in a different way, because the bone transform will be already applied to the modelview matrix.
 		</member>
-		<member name="rendering/quality/spatial_partitioning/render_tree_balance" type="float" setter="" getter="" default="0.17">
+		<member name="rendering/quality/spatial_partitioning/render_tree_balance" type="float" setter="" getter="" default="0.0">
 			The rendering octree balance can be changed to favor smaller ([code]0[/code]), or larger ([code]1[/code]) branches.
 			Larger branches can increase performance significantly in some projects.
 		</member>

servers/visual_server.cpp

@@ -2441,7 +2441,7 @@ VisualServer::VisualServer() {
 	GLOBAL_DEF("rendering/quality/skinning/force_software_skinning", false);
 
 	const char *sz_balance_render_tree = "rendering/quality/spatial_partitioning/render_tree_balance";
-	GLOBAL_DEF(sz_balance_render_tree, 0.17f);
+	GLOBAL_DEF(sz_balance_render_tree, 0.0f);
 	ProjectSettings::get_singleton()->set_custom_property_info(sz_balance_render_tree, PropertyInfo(Variant::REAL, sz_balance_render_tree, PROPERTY_HINT_RANGE, "0.0,1.0,0.01"));
 
 	GLOBAL_DEF("rendering/quality/2d/use_software_skinning", true);