Updated GDScript example to use clear_surfaces() and C Sharp example to use ClearSurfaces() instead of non-existent surface_remove() and SurfaceRemove()

doc/classes/MeshDataTool.xml

@@ -19,7 +19,7 @@
 		    vertex += mdt.get_vertex_normal(i)
 		    # Save your change.
 		    mdt.set_vertex(i, vertex)
-		mesh.surface_remove(0)
+		mesh.clear_surfaces()
 		mdt.commit_to_surface(mesh)
 		var mi = MeshInstance.new()
 		mi.mesh = mesh
@@ -38,7 +38,7 @@
 		    // Save your change.
 		    mdt.SetVertex(i, vertex);
 		}
-		mesh.SurfaceRemove(0);
+		mesh.ClearSurfaces();
 		mdt.CommitToSurface(mesh);
 		var mi = new MeshInstance();
 		mi.Mesh = mesh;