Fix Ethernaut's `Delegation` exploit

[leovct]

$ forge test -vvv --match-contract Delegation                                                                                                                                                      
[⠊] Compiling...
No files changed, compilation skipped

Ran 1 test for test/Ethernaut/DelegationExploit.t.sol:DelegationExploit
[FAIL. Reason: assertion failed] testExploit() (gas: 37866)
Logs:
  Target contract deployed
  Current owner: 0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946
  New owner: 0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946
  Error: a == b not satisfied [address]
        Left: 0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946
       Right: 0x5Bf3eeB5560eEACC941C553320999006D27dD42b

Traces:
  [37866] DelegationExploit::testExploit()
    ├─ [2303] Delegation::owner() [staticcall]
    │   └─ ← [Return] deployer: [0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946]
    ├─ [0] console::log("Current owner: %s", deployer: [0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946]) [staticcall]
    │   └─ ← [Stop] 
    ├─ [0] VM::startPrank(exploiter: [0x5Bf3eeB5560eEACC941C553320999006D27dD42b])
    │   └─ ← [Return] 
    ├─ [4983] Delegation::pwn()
    │   ├─ [0] exploiter::pwn() [delegatecall]
    │   │   └─ ← [Stop] 
    │   └─ ← [Stop] 
    ├─ [0] VM::stopPrank()
    │   └─ ← [Return] 
    ├─ [303] Delegation::owner() [staticcall]
    │   └─ ← [Return] deployer: [0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946]
    ├─ [0] console::log("New owner: %s", deployer: [0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946]) [staticcall]
    │   └─ ← [Stop] 
    ├─ emit log(val: "Error: a == b not satisfied [address]")
    ├─ emit log_named_address(key: "      Left", val: deployer: [0xaE0bDc4eEAC5E950B67C6819B118761CaAF61946])
    ├─ emit log_named_address(key: "     Right", val: exploiter: [0x5Bf3eeB5560eEACC941C553320999006D27dD42b])
    ├─ [0] VM::store(VM: [0x7109709ECfa91a80626fF3989D68f67F5b1DD12D], 0x6661696c65640000000000000000000000000000000000000000000000000000, 0x0000000000000000000000000000000000000000000000000000000000000001)
    │   └─ ← [Return] 
    └─ ← [Stop] 

Suite result: FAILED. 0 passed; 1 failed; 0 skipped; finished in 582.42µs (94.83µs CPU time)

Ran 1 test suite in 167.48ms (582.42µs CPU time): 0 tests passed, 1 failed, 0 skipped (1 total tests)

Failing tests:
Encountered 1 failing test in test/Ethernaut/DelegationExploit.t.sol:DelegationExploit
[FAIL. Reason: assertion failed] testExploit() (gas: 37866)

Encountered a total of 1 failing tests, 0 tests succeeded