docs: fix return value type in docstring

[alexander-held]

Small fix for consistency: np.ndarray is the correct return value type of visualize._total_yield_uncertainty instead of np.array. The type hint was already correct.

* fix return value type in docstring of visualize._total_yield_uncertainty

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (fde48f1) 100.00% compared to head (841e8b1) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #411 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 22 22 Lines 2069 2069 Branches 334 334 ========================================= Hits 2069 2069 ``` | [Impacted Files](https://app.codecov.io/gh/scikit-hep/cabinetry/pull/411?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scikit-hep) | Coverage Δ | | |---|---|---| | [src/cabinetry/visualize/\_\_init\_\_.py](https://app.codecov.io/gh/scikit-hep/cabinetry/pull/411?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scikit-hep#diff-c3JjL2NhYmluZXRyeS92aXN1YWxpemUvX19pbml0X18ucHk=) | `100.00% <ø> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.