message: Fix the error of protocol explain in "book/src/plonk/inner_product.md"
diff: @@ -113,6 +113,7 @@ We can picture the protocol as follows:
  1. The prover first sends a commitment to the polynomial $f$.
  2. The verifier sends a point $s$, asking for the value $f(s)$. To help the prover perform a proof of correct evaluation, they also send a random challenge $x$.
  +(NOTE: The verifier sends the random challenge $x$ ONLY AFTER they receive the $z=f(s)$)
  3. The prover sends the result of the evaluation, $z$, as well as a proof.
  ![inner 1](../img/inner1.png)
  