fix typo in config option description

Kudos @iBicha
https://github.com/PurpleI2P/i2pd/pull/1662#pullrequestreview-687850246

Signed-off-by: R4SAS <r4sas@i2pmail.org>

libi2pd/Config.cpp

@@ -285,7 +285,7 @@ namespace config {
 
 		options_description meshnets("Meshnet transports options");
 		meshnets.add_options()
-			("meshnets.yggdrasil", bool_switch()->default_value(false),              "Support transports through the Yggdrasil (deafult: false)")
+			("meshnets.yggdrasil", bool_switch()->default_value(false),              "Support transports through the Yggdrasil (default: false)")
 			("meshnets.yggaddress", value<std::string>()->default_value(""),         "Yggdrasil address to publish")
 		;