Base: Add sysctl man page

Author: https://github.com/bcoles
Commit: 69b98f7d32
Pull-request: https://github.com/SerenityOS/serenity/pull/5689
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/emanuele6

Userland/Utilities/sysctl.cpp

@@ -117,7 +117,7 @@ int main(int argc, char** argv)
     args_parser.set_general_help(
         "Show or modify system-internal values. This requires root, and can crash your system.");
     args_parser.add_option(show_all, "Show all variables", nullptr, 'a');
-    args_parser.add_positional_argument(var, "Command (var[=value])", "command", Core::ArgsParser::Required::No);
+    args_parser.add_positional_argument(var, "variable[=value]", "variable", Core::ArgsParser::Required::No);
     args_parser.parse(argc, argv);
 
     if (var == nullptr) {