cli: Reject arguments to -getinfo

Currently it's possible to accidentally type e.g.

    bitcoin-cli -getinfo getbalance

and get an answer which can be confusing; the trialing arguments are
just ignored.

To avoid this, throw an error if the user provides arguments to
`-getinfo`.

src/bitcoin-cli.cpp

@@ -213,6 +213,9 @@ public:
     /** Create a simulated `getinfo` request. */
     UniValue PrepareRequest(const std::string& method, const std::vector<std::string>& args) override
     {
+        if (!args.empty()) {
+            throw std::runtime_error("-getinfo takes no arguments");
+        }
         UniValue result(UniValue::VARR);
         result.push_back(JSONRPCRequestObj("getnetworkinfo", NullUniValue, ID_NETWORKINFO));
         result.push_back(JSONRPCRequestObj("getblockchaininfo", NullUniValue, ID_BLOCKCHAININFO));