fix: update minimum Cardano node version for sanchonet in networks file

From '8.12.0-pre' to '8.11.0-pre' following networking issues.

Author: jpraynaud

networks.json

@@ -114,7 +114,7 @@
   },
   "sanchonet": {
     "cardano-minimum-version": {
-      "mithril-signer": "8.12.0-pre"
+      "mithril-signer": "8.11.0-pre"
     },
     "mithril-networks": [
       {