correct typo in docs

[VictorVanthilt]

I was reading the documentation for "Bosonic tensor contractions and tensor networks" and stumbled upon "triival" which I think should be "trivial".

Sidenote: the sections on fermionic and anyonic tensor contractions, right below the section I was reading, which are now marked as TODO would be very very helpful.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.63%. Comparing base (9bd4c40) to head (9b0226f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #231   +/-   ##
=======================================
  Coverage   82.63%   82.63%           
=======================================
  Files          43       43           
  Lines        5557     5557           
=======================================
  Hits         4592     4592           
  Misses        965      965           

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