Docs: Fix SurfaceTool example caps typo

(cherry picked from commit 6719fea8dcb820bd90f7c77065e658d384ac709a)

doc/classes/SurfaceTool.xml

@@ -17,7 +17,7 @@
 		var st = new SurfaceTool();
 		st.Begin(Mesh.PrimitiveType.Triangles);
 		st.SetColor(new Color(1, 0, 0));
-		st.SetUv(new Vector2(0, 0));
+		st.SetUV(new Vector2(0, 0));
 		st.AddVertex(new Vector3(0, 0, 0));
 		[/csharp]
 		[/codeblocks]