fix(Makefile): remove redundant command parameter

Fixes a benign typo in the Makefile.

```console
gradishar:deis matt$ fleetctl list-machines --no-legend --full list-machines
6c3c799c74cf4a4aac39004149b50cf9	172.17.8.102	-
c32f3d6d37b54c7e8059755952cce476	172.17.8.104	-
c41100bfb86b4c2580e7c6089eabae48	172.17.8.103	-
e43e5bd63a2a4b608cec52928be076c8	172.17.8.101	-
gradishar:deis matt$ fleetctl list-machines --no-legend --full
6c3c799c74cf4a4aac39004149b50cf9	172.17.8.102	-
c32f3d6d37b54c7e8059755952cce476	172.17.8.104	-
c41100bfb86b4c2580e7c6089eabae48	172.17.8.103	-
e43e5bd63a2a4b608cec52928be076c8	172.17.8.101	-
```