Fix USD symbol

Author: timmygee

forex_python/raw_data/currencies.json

@@ -144,7 +144,7 @@
   {"cc":"TZS","symbol":"TZS","name":"Tanzanian shilling"},
   {"cc":"UAH","symbol":"UAH","name":"Ukrainian hryvnia"},
   {"cc":"UGX","symbol":"USh","name":"Ugandan shilling"},
-  {"cc":"USD","symbol":"US$","name":"United States dollar"},
+  {"cc":"USD","symbol":"$","name":"United States dollar"},
   {"cc":"UYU","symbol":"$U","name":"Uruguayan peso"},
   {"cc":"UZS","symbol":"UZS","name":"Uzbekistani som"},
   {"cc":"VEB","symbol":"Bs","name":"Venezuelan bolivar"},