Remove zeroing in similar for Hermitian

[jishnub]

The comment suggests that the Hermitian constructor used to ensure that the parent had a real diagonal. It doesn't anymore, so the explicit fill may be removed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.89%. Comparing base (51923a5) to head (7980baf).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1455      +/-   ##
==========================================
- Coverage   93.89%   93.89%   -0.01%     
==========================================
  Files          34       34              
  Lines       15934    15931       -3     
==========================================
- Hits        14961    14958       -3     
  Misses        973      973              

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