Promote spaces for BraidingTensor

[lkdvos]

This is a small change for fixing QuantumKitHub/MPSKit.jl#307

It's mostly about working with SumSpace and non-SumSpace instances so I'm not sure if I have meaningful tests here.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 82.85%. Comparing base (6fd09bc) to head (bb54699).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/tensors/braidingtensor.jl	33.33%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #258      +/-   ##
==========================================
- Coverage   82.91%   82.85%   -0.07%     
==========================================
  Files          44       44              
  Lines        5754     5757       +3     
==========================================
- Hits         4771     4770       -1     
- Misses        983      987       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.