Noncontextual check fix

[AlexisRalli]

-fixed bug in is_noncontextual in PauliwordOp

[codecov-commenter]

Codecov Report

Patch coverage: 67.56% and project coverage change: -0.16% :warning:

Comparison is base (2f98191) 77.33% compared to head (c9f6bc0) 77.18%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #156 +/- ## ========================================== - Coverage 77.33% 77.18% -0.16% ========================================== Files 33 33 Lines 3750 3826 +76 ========================================== + Hits 2900 2953 +53 - Misses 850 873 +23 ``` | [Files Changed](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS) | Coverage Δ | | |---|---|---| | [symmer/operators/noncontextual\_op.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-c3ltbWVyL29wZXJhdG9ycy9ub25jb250ZXh0dWFsX29wLnB5) | `75.53% <37.93%> (-7.40%)` | :arrow_down: | | [symmer/operators/anticommuting\_op.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-c3ltbWVyL29wZXJhdG9ycy9hbnRpY29tbXV0aW5nX29wLnB5) | `82.22% <100.00%> (+0.13%)` | :arrow_up: | | [symmer/operators/base.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-c3ltbWVyL29wZXJhdG9ycy9iYXNlLnB5) | `65.52% <100.00%> (+1.11%)` | :arrow_up: | | [symmer/operators/utils.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-c3ltbWVyL29wZXJhdG9ycy91dGlscy5weQ==) | `77.58% <100.00%> (-0.07%)` | :arrow_down: | | [symmer/utils.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-c3ltbWVyL3V0aWxzLnB5) | `78.91% <100.00%> (+7.87%)` | :arrow_up: | | [tests/test\_operators/test\_base.py](https://app.codecov.io/gh/UCL-CCS/symmer/pull/156?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=UCL-CCS#diff-dGVzdHMvdGVzdF9vcGVyYXRvcnMvdGVzdF9iYXNlLnB5) | `99.65% <100.00%> (+<0.01%)` | :arrow_up: |

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