Consistency for NodePath doc code examples

[gio3k]

Just makes a code example in NodePath.xml similar to the others

[akien-mga]

Confirmed to be the only occurrence of that specific example:

$ rg -g'*.xml' "var nodepath"
doc/classes/NodePath.xml
104:                            var nodepath = NodePath("Path2D/PathFollow2D/Sprite2D:texture:load_path")
108:                            var nodepath = new NodePath("Path2D/PathFollow2D/Sprite2D:texture:load_path");
$ rg -g'*.xml' "var node_path"
doc/classes/NodePath.xml
77:                             var node_path = NodePath("position:x")
121:                            var node_path = NodePath("Path2D/PathFollow2D/Sprite2D")
149:                            var node_path = NodePath("Path2D/PathFollow2D/Sprite2D:texture:load_path")

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉