[rpc] changed MineBlocksOnDemand to IsMockableChain

Author: glozow

src/rpc/misc.cpp

@@ -345,8 +345,9 @@ static UniValue setmocktime(const JSONRPCRequest& request)
                 RPCExamples{""},
             }.Check(request);
 
-    if (!Params().MineBlocksOnDemand())
-        throw std::runtime_error("setmocktime for regression testing (-regtest mode) only");
+    if (!Params().IsMockableChain()) {
+        throw std::runtime_error("setmocktime is for regression testing (-regtest mode) only");
+    }
 
     // For now, don't change mocktime if we're in the middle of validation, as
     // this could have an effect on mempool time-based eviction, as well as