Raise exception instead of warning when multichannel audio has wrong shape

[iver56]

https://github.com/iver56/audiomentations/issues/274

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (8f9bfd5) 96.57% compared to head (78b650f) 96.57%.

:exclamation: Current head 78b650f differs from pull request most recent head c76df2d. Consider uploading reports for the commit c76df2d to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #276 +/- ## ======================================= Coverage 96.57% 96.57% ======================================= Files 44 44 Lines 1779 1781 +2 ======================================= + Hits 1718 1720 +2 Misses 61 61 ``` | [Impacted Files](https://app.codecov.io/gh/iver56/audiomentations/pull/276?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Iver+Jordal) | Coverage Δ | | |---|---|---| | [audiomentations/core/transforms\_interface.py](https://app.codecov.io/gh/iver56/audiomentations/pull/276?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Iver+Jordal#diff-YXVkaW9tZW50YXRpb25zL2NvcmUvdHJhbnNmb3Jtc19pbnRlcmZhY2UucHk=) | `93.65% <100.00%> (+0.20%)` | :arrow_up: |

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