Remove includeconf nested scope

Easier to review ignoring whitespace

Suggestion from John Newbery <john@johnnewbery.com> in
https://github.com/bitcoin/bitcoin/pull/15934#discussion_r343806860

src/util/system.cpp

@@ -939,7 +939,6 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
 
             // Warn about recursive -includeconf
             conf_file_names = GetArgs("-includeconf");
-            {
             std::vector<std::string> includeconf_net(GetArgs(std::string("-") + chain_id + ".includeconf"));
             conf_file_names.insert(conf_file_names.end(), includeconf_net.begin(), includeconf_net.end());
             std::string chain_id_final = GetChainName();
@@ -948,7 +947,6 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
                 includeconf_net = GetArgs(std::string("-") + chain_id_final + ".includeconf");
                 conf_file_names.insert(conf_file_names.end(), includeconf_net.begin(), includeconf_net.end());
             }
-            }
             for (const std::string& conf_file_name : conf_file_names) {
                 tfm::format(std::cerr, "warning: -includeconf cannot be used from included files; ignoring -includeconf=%s\n", conf_file_name);
             }