Cell cleanup: dead code

[CivBase]

Description:
Removed some dead code I found in cell.py. It is technically executed, but it is also overridden immediately after and does not affect the code in any meaningful way.

Reviewer(s):
@nskinkel

[coveralls]

Coverage increased (+0.01%) to 35.9% when pulling 4aedc01 on CivBase:clean_up_dead_code into 44441db on nskinkel:master.

[nskinkel]

Good catch. I fixed this slightly differently than you did in your PR in 096cf92, but same idea. I prefer to assign things using meaningful constants where possible to help readers understand how we implement the protocol, so I just did that and removed the struct.calcsize() call entirely.