Update crowdsales.adoc fix invalid conversion (#2026)
Update crowdsales.adoc fix invalid conversion (#2026)

Code sample for MyCrowdsaleDeployer causes TypeError:
```
browser/MyCrowdsaleDeployer.sol:21:13: TypeError: Invalid type for argument in function call. 
Invalid implicit conversion from address to contract IERC20 requested.
            address(token)            // the token
            ^------------^
```
Change: 
```solidity
address(token)   // the token
```
To:
```solidity
token   // the token
```

Reported by community member in the forum: https://forum.openzeppelin.com/t/invalid-implicit-conversion-from-address-to-contract-ierc20-requested/1937
OpenZeppelin/zep-solidity,OpenZeppelin/zeppelin-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity,OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts