Update fip-0059 synthetic challenge generation function (#951)

* Update fip-0059.md 

Updating the synthetic challenge generation function (it was changed during the code audit but at the time we forgot to update the fip, so I am doing it now)

* Update fip-0059.md

FIPS/fip-0059.md

@@ -74,8 +74,10 @@ Differences between currently deployed PoRep and Synthetic PoRep are limited to
     - `N_syn` set to $2^{18}$;
     - `N_verified` set to 176 (same as current *N_porep_challenges) ;
 - New challenge generation functions.
-    - <img src="https://user-images.githubusercontent.com/55720287/232783448-4629ea36-9f37-4b14-8971-bcad314700ab.png" width="400">
-    - Note that we have determined using ChaCha20 in the place of Sha256 is preferred.
+
+    <img src="https://github.com/filecoin-project/FIPs/assets/23217773/dee09666-5ba8-41cf-befc-f043cd2e61bf" width="400">
+
+    Note that we have determined using ChaCha20 in the place of Sha256 is preferred.
 - Proof construction and verification can use the same functions as today.
 
 Synthetic PoRep, while likely enabled by default after it's available, is an _optional_ feature that can be opt-out for those interested.  The previously available proofs types can be used to continue the PoRep behaviour.
@@ -129,7 +131,7 @@ Note that, assuming PC1 takes almost 3h and we have 150 epochs between PreCommit
 
 ## Implementations
 
-Implementation in progress.
+See the tracking issue [filecoin-project/lotus#10984](https://github.com/filecoin-project/lotus/issues/10984).
 
 ## Copyright Waiver