remove unnecessary warning = FALSE from zambia_solution chunk

The warning is emitted by load_survey(), not contact_matrix(),
so suppressing it on the contact_matrix() chunk has no effect.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: avallecam

episodes/contact-matrices.Rmd

@@ -201,7 +201,7 @@ Similar to the code above, to access vector values within a dataframe, you can u
 
 :::::::::::::::::::::::: instructor 
 
-```{r zambia_solution, message = FALSE, warning = FALSE}
+```{r zambia_solution}
 # Generate the contact matrix for Zambia only
 contacts_byage_zambia <- socialmixr::contact_matrix(
   survey = zambia_sa_survey,