doc: Update comments for new chain settings (-signet and -chain=signet)

src/bitcoin-wallet.cpp

@@ -62,7 +62,7 @@ static bool WalletAppInit(int argc, char* argv[])
         tfm::format(std::cerr, "Error: Specified data directory \"%s\" does not exist.\n", gArgs.GetArg("-datadir", ""));
         return false;
     }
-    // Check for -testnet or -regtest parameter (Params() calls are only valid after this clause)
+    // Check for chain settings (Params() calls are only valid after this clause)
     SelectParams(gArgs.GetChainName());
 
     return true;