Add distance_transform_edt to transforms.__init__ (#7100)

Forgot the import of the helper function `distance_transform_edt` in
`transforms.__init__`

### Types of changes
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applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [ ] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [ ] Quick tests passed locally by running `./runtests.sh --quick
--unittests --disttests`.
- [ ] In-line docstrings updated.
- [ ] Documentation updated, tested `make html` command in the `docs/`
folder.

Signed-off-by: Matthias Hadlich <matthiashadlich@posteo.de>

Author: matt3o

monai/transforms/__init__.py

@@ -641,6 +641,7 @@
     create_scale,
     create_shear,
     create_translate,
+    distance_transform_edt,
     equalize_hist,
     extreme_points_to_image,
     generate_label_classes_crop_centers,