Merge bitcoin#28874: doc: fixup help output for -upnp and -natpmp

92f88a9 doc: fixup NAT-PMP help doc (fanquake)
02395ed init: remove redundant upnp #ifdef (fanquake)

Pull request description:

  This is a very belated followup to bitcoin#26896 (which removed the configure options for setting the upnp and natpmp runtime default) and corrects the `-help` docs for `-upnp` and `-natpmp`.

ACKs for top commit:
  davidgumberg:
    ACK bitcoin@92f88a9
  hernanmarino:
    ACK 92f88a9

Tree-SHA512: 795dc8a8703bf322b5831d845de85f2428ee0dd45d3064b48ff47d147147381af26c0a9d00c596db12009b254763844b209989daf4e7470d20e8a1753b640966

Author: fanquake

src/init.cpp

@@ -589,16 +589,12 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-torcontrol=<ip>:<port>", strprintf("Tor control port to use if onion listening enabled (default: %s)", DEFAULT_TOR_CONTROL), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-torpassword=<pass>", "Tor control port password (default: empty)", ArgsManager::ALLOW_ANY | ArgsManager::SENSITIVE, OptionsCategory::CONNECTION);
 #ifdef USE_UPNP
-#if USE_UPNP
-    argsman.AddArg("-upnp", "Use UPnP to map the listening port (default: 1 when listening and no -proxy)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
-#else
-    argsman.AddArg("-upnp", strprintf("Use UPnP to map the listening port (default: %u)", 0), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
-#endif
+    argsman.AddArg("-upnp", strprintf("Use UPnP to map the listening port (default: %u)", DEFAULT_UPNP), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
 #else
     hidden_args.emplace_back("-upnp");
 #endif
 #ifdef USE_NATPMP
-    argsman.AddArg("-natpmp", strprintf("Use NAT-PMP to map the listening port (default: %s)", DEFAULT_NATPMP ? "1 when listening and no -proxy" : "0"), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
+    argsman.AddArg("-natpmp", strprintf("Use NAT-PMP to map the listening port (default: %u)", DEFAULT_NATPMP), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
 #else
     hidden_args.emplace_back("-natpmp");
 #endif // USE_NATPMP