fix: global table update message hash (#1460)

**Motivation:**

The `messageHash` in the certificate for
`operatorTableUpdater.updateGlobalTableRoot` should be a properly
formatted type hash that takes into account the `referenceTimestamp` and
`globalTableRoot`, so neither can be spoofed.

**Modifications:**

Checks that
```solidity
        require(
            globalTableRootCert.messageHash == getGlobalTableUpdateMessageHash(globalTableRoot, referenceTimestamp),
            InvalidMessageHash()
        );
```

**Result:**

Correct Code

Author: ypatil12