CRegTestParams: Use args instead of gArgs.

src/chainparams.cpp

@@ -423,7 +423,7 @@ public:
         pchMessageStart[2] = 0xb5;
         pchMessageStart[3] = 0xda;
         nDefaultPort = 18444;
-        nPruneAfterHeight = gArgs.GetBoolArg("-fastprune", false) ? 100 : 1000;
+        nPruneAfterHeight = args.GetBoolArg("-fastprune", false) ? 100 : 1000;
         m_assumed_blockchain_size = 0;
         m_assumed_chain_state_size = 0;