remove dead rpc code

Checking for fHelp, or the size of the args, is dead code because:
* fHelp is always false (src/qt/test/rpcnestedtests.cpp)
* It is already implicitly called by RPCHelpMan::Check
  (src/rpc/mining.cpp, src/rpc/misc.cpp, src/rpc/net.cpp)

Author: MarcoFalke

src/qt/test/rpcnestedtests.cpp

@@ -16,9 +16,6 @@
 
 static UniValue rpcNestedTest_rpc(const JSONRPCRequest& request)
 {
-    if (request.fHelp) {
-        return "help message";
-    }
     return request.params.write(0, 0);
 }
 

src/rpc/mining.cpp

@@ -242,12 +242,7 @@ static RPCHelpMan generatetodescriptor()
 static RPCHelpMan generate()
 {
     return RPCHelpMan{"generate", "has been replaced by the -generate cli option. Refer to -help for more information.", {}, {}, RPCExamples{""}, [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
-
-    if (request.fHelp) {
-        throw std::runtime_error(self.ToString());
-    } else {
         throw JSONRPCError(RPC_METHOD_NOT_FOUND, self.ToString());
-    }
     }};
 }
 

src/rpc/misc.cpp

@@ -624,8 +624,6 @@ static RPCHelpMan echo(const std::string& name)
                 RPCExamples{""},
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    if (request.fHelp) throw std::runtime_error(self.ToString());
-
     if (request.params[9].isStr()) {
         CHECK_NONFATAL(request.params[9].get_str() != "trigger_internal_bug");
     }

src/rpc/net.cpp

@@ -262,10 +262,10 @@ static RPCHelpMan addnode()
     std::string strCommand;
     if (!request.params[1].isNull())
         strCommand = request.params[1].get_str();
-    if (request.fHelp || request.params.size() != 2 ||
-        (strCommand != "onetry" && strCommand != "add" && strCommand != "remove"))
+    if (strCommand != "onetry" && strCommand != "add" && strCommand != "remove") {
         throw std::runtime_error(
             self.ToString());
+    }
 
     NodeContext& node = EnsureNodeContext(request.context);
     if(!node.connman)
@@ -604,7 +604,7 @@ static RPCHelpMan setban()
     std::string strCommand;
     if (!request.params[1].isNull())
         strCommand = request.params[1].get_str();
-    if (request.fHelp || !help.IsValidNumArgs(request.params.size()) || (strCommand != "add" && strCommand != "remove")) {
+    if (strCommand != "add" && strCommand != "remove") {
         throw std::runtime_error(help.ToString());
     }
     NodeContext& node = EnsureNodeContext(request.context);