Renames `metadata/annotations/anatomy` from `cardiac` to `heart` in the 25 files of `technion/cardiac/data/`, to match the label used elsewhere in OpenH-RF (e.g. `tue-cardiac`, `oslo`, `vanderbilt`). The existing attributes are kept.
Files changed: 25. Only `metadata/annotations/anatomy` was written, as variable-length strings carrying the same `description`/`unit` attributes as the sibling files that already hold these fields. `raw_data` and all other metadata are untouched.
Diff:
```
technion/cardiac/data/a1.hdf5: differs (main)
~ metadata/annotations/anatomy: 'cardiac' -> 'heart'
technion/cardiac/data/a2.hdf5: differs (main)
~ metadata/annotations/anatomy: 'cardiac' -> 'heart'
technion/cardiac/data/a3.hdf5: differs (main)
~ metadata/annotations/anatomy: 'cardiac' -> 'heart'
technion/cardiac/data/a4.hdf5: differs (main)
~ metadata/annotations/anatomy: 'cardiac' -> 'heart'
technion/cardiac/data/a5.hdf5: differs (main)
~ metadata/annotations/anatomy: 'cardiac' -> 'heart'
t…
