okcoin: Remove exchange implementation (#1626)

* okcoin: Remove exchange implementation

* exchanges/order: Rid TradeMode from Submit type

docs/ADD_NEW_EXCHANGE.md

@@ -217,7 +217,6 @@ Yes means supported, No means not yet implemented and NA means protocol unsuppor
 | Kraken | Yes | Yes | NA |
 | Kucoin | Yes | Yes | No |
 | Lbank | Yes | No | NA |
-| Okcoin | Yes | Yes | No |
 | Okx | Yes | Yes | NA |
 | Poloniex | Yes | Yes | NA |
 | Yobit | Yes | NA | NA |
@@ -247,7 +246,6 @@ var Exchanges = []string{
 	"kraken",
 	"kucoin",
 	"lbank",
-	"okcoin",
 	"okx",
 	"poloniex",
 	"yobit",

docs/MULTICHAIN_TRANSFER_SUPPORT.md

@@ -64,7 +64,6 @@ $ ./gctcli withdrawcryptofunds --exchange=binance --currency=USDT --address=TJU9
 | Kraken | Yes | Yes | Front-end and API don't match total available transfer chains |
 | Kucoin |  Yes | Yes | |
 | Lbank | No | No | |
-| Okcoin | Yes | Yes | |
 | Okx | Yes | Yes | |
 | Poloniex | Yes | Yes | |
 | Yobit | No | No | |

docs/OHLCV.md

@@ -86,7 +86,6 @@ A helper tool [cmd/dbseed](../cmd/dbseed/README.md) has been created for assisti
 | Kraken         | Y           |
 | Kucoin         | Y           |                 
 | lBank          | Y           |                
-| Okcoin         | Y           |  
 | Okx            | Y           |         
 | Poloniex       | Y           |          
 | Yobit          |             |