Adjust testdev chain to new prefix - STM

beemgraphenebase/chains.py

@@ -54,7 +54,7 @@ known_chains = {
         "chain_id":
         "18dcf0a285365fc58b71f18b3d3fec954aa0c141c44e4e5cb4cf777b9eab274e",
         "min_version": '0.20.0',
-        "prefix": "TST",
+        "prefix": "STM",
         "chain_assets": [
             {"asset": "@@000000013", "symbol": "TBD", "precision": 3, "id": 0},
             {"asset": "@@000000021", "symbol": "TESTS", "precision": 3, "id": 1},