Update virtual account with unit test

[ankitdas13]

For addReceiver : https://github.com/razorpay/razorpay-node/blob/master/documents/virtualAccount.md#add-receiver-to-an-existing-virtual-account Link : https://razorpay.com/docs/api/payments/smart-collect-tpv/#add-receiver-to-an-existing-virtual-account

For allowedPayer : https://github.com/razorpay/razorpay-node/blob/master/documents/virtualAccount.md#add-an-allowed-payer-account Link : https://razorpay.com/docs/api/payments/smart-collect-tpv/#add-an-allowed-payer-account

for deleteAllowedPayer : https://github.com/razorpay/razorpay-node/blob/master/documents/virtualAccount.md#delete-an-allowed-payer-account Link : https://razorpay.com/docs/api/payments/smart-collect-tpv/#delete-an-allowed-payer-account

[sonyy-m]

https://github.com/razorpay/razorpay-ruby/blob/3c49f01224f8e65bee3d58d9e9d42787388a1650/lib/razorpay/virtual_account.rb#L24-L26 Update closemethod according to the api doc https://razorpay.com/docs/api/payments/smart-collect-tpv/#close-a-virtual-account status is not required and the request method is POST