docs: deploy correct contract in usage tutorial (#79)

README.md

@@ -92,7 +92,7 @@ contract BaseTest is Test, SmockHelper {
  // return _greeterAddress;
 
  greeter = MockGreeter(
- deployMock('Greeter', type(Greeter).creationCode, abi.encode('Hello'))
+ deployMock('Greeter', type(MockGreeter).creationCode, abi.encode('Hello'))
  );
  }
 }