Remove a todo.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -11245,8 +11245,8 @@ The same \quadraticConstraintProgram is used for compression and decompression.
 
 \pnote{
 The point-on-curve check could be omitted if $(u, \varv)$ were already known to be on the curve.
-However, the \Sapling circuit never omits it \todo{CHECK}; this provides a redundant consistency
-check on the elliptic curve arithmetic in some cases.
+However, the \Sapling circuit never omits it; this provides a consistency check on the elliptic
+curve arithmetic.
 }