Fix translation in Lattice

[chrisjonesBSU]

I found a box where the translation of the 2nd chain in the unit cell of Lattice was not being translated correctly. This should fix that

[codecov]

Codecov Report

Merging #74 (b03116b) into main (a9269b8) will increase coverage by 0.12%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head b03116b differs from pull request most recent head 88d4958. Consider uploading reports for the commit 88d4958 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #74      +/-   ##
==========================================
+ Coverage   93.73%   93.86%   +0.12%     
==========================================
  Files          20       20              
  Lines        1533     1531       -2     
==========================================
  Hits         1437     1437              
+ Misses         96       94       -2     

Files	Coverage Δ
flowermd/base/system.py	90.61% <100.00%> (ø)

... and 1 file with indirect coverage changes