Update TensorKit v0.14

[lkdvos]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.38%. Comparing base (d7e11e2) to head (1de458f).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #16      +/-   ##
==========================================
- Coverage   73.42%   73.38%   -0.05%     
==========================================
  Files           5        5              
  Lines         621      620       -1     
==========================================
- Hits          456      455       -1     
  Misses        165      165              

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[lkdvos]

@Jutho , I made some changes here to ensure compatibility with both TensorKit v0.13 and v0.14. I would propose merging this and tagging it as a non-breaking change, and afterwards we could consider moving to TensorKit v0.14 definitively and actually enforcing that S is diagonal, which also improves some of the code assumptions at the bottom of the grassmann file.
(I require something compatible with v0.14 to start using SUNRepresentations with MPSKit, since multiplicity fusion is broken in v0.13)