fix(initchain): Enforce stricter handling on InitChain Requests

[rezbera]

The original code for handling []ValidatorUpdate was copied from CosmosSDK. In our case, the ValidatorUpdate list is ALWAYS expected to be 0 in initChain as we derive the validator set from the deposits directly in InitChain, which is the source of truth.

Therefore, we can remove the additional handling if the len([]ValidatorUpdate) > 0 and simply enforce that it is always zero length, reducing confusion around its purpose

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 21.17%. Comparing base (419cd66) to head (2537927).
Report is 1 commits behind head on main.

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HEAD has 3 uploads less than BASE

Flag	BASE (419cd66)	HEAD (2537927)
	4	1

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2413      +/-   ##
==========================================
- Coverage   27.08%   21.17%   -5.91%     
==========================================
  Files         351        3     -348     
  Lines       15543       85   -15458     
  Branches       20       20              
==========================================
- Hits         4210       18    -4192     
+ Misses      11130       66   -11064     
+ Partials      203        1     -202     

see 348 files with indirect coverage changes

[abi87]

lgtm