C#: Remove Plane section from C# differences page

tutorials/scripting/c_sharp/c_sharp_differences.rst

@@ -406,17 +406,6 @@ GDScript              C#
 ``get_scale()``       ``Scale``
 ====================  ==============================================================
 
-Plane
------
-
-The following method was converted to a property with a *slightly* different name:
-
-================  ==================================================================
-GDScript          C#
-================  ==================================================================
-``center()``      ``Center``
-================  ==================================================================
-
 Rect2
 -----