message: [book] fix img path (bis)
diff: A polynomial commitment is a scheme that allows you to commit to a polynomial (i.e. to its coefficients). Later, someone can ask you to evaluate the polynomial at some point and give them the result, which you can do as well as provide a proof of correct evaluation.
  -<img src="../../img/polycom.png" width="600px">
  +<img src="../img/polycom.png" width="600px">
  ## Schwartz-Zippel lemma
  