Update 062submit_withdraw example as it's currently confusing

[TBG90]

The example in 062submit_withdraw (https://github.com/coinexcom/coinex_exchange_api/wiki/062submit_withdraw) suggests that the access_id and tonce should be part of the request URL, whereas they are part of the request body; suggest that the wiki page is updated in line with 031limit_order (https://github.com/coinexcom/coinex_exchange_api/wiki/031limit_order) for clarity, i.e. that the request URL is just https://api.coinex.com/v1/balance/coin/withdraw and an example request body could be:

Request.Body

{
"access_id":" BFFA64957AA240F6BBEA26F4E07EC0D9",
"actual_amount": "56.5",
"coin_address": "xyz",
"coin_type": "BTC",
"tonce": 1513746038205,
"transfer_method": "onchain"
}