chore: Remove outdated doctesting stuff

CONTRIBUTING.md

@@ -104,10 +104,9 @@ uv run pre-commit install
      uv run make doctest -C docs
      ```
 
-  - To compute the code coverage locally, you should run the unit tests and the doc tests together,
-  with the `--cov` flag:
+  - To compute the code coverage locally, you should run the unit tests with the `--cov` flag:
     ```bash
-    uv run pytest tests/unit tests/doc --cov=src
+    uv run pytest tests/unit --cov=src
     ```
 
     > [!TIP]
@@ -148,8 +147,7 @@ should create it.
 ### Testing
 
 We ask contributors to implement the unit tests necessary to check the correctness of their
-implementations. Besides, whenever usage examples are provided, we require the example's code to be
-tested in `tests/doc`. We aim for 100% code coverage, but we greatly appreciate any PR, even with
+implementations. We aim for 100% code coverage, but we greatly appreciate any PR, even with
 insufficient code coverage. To ensure that the tensors generated during the tests are on the right
 device and dtype, you have to use the partial functions defined in `tests/utils/tensors.py` to
 instantiate tensors. For instance, instead of

pyproject.toml

@@ -163,7 +163,6 @@ ignore = [
 
 [tool.ruff.lint.per-file-ignores]
 "**/conftest.py" = ["ARG"]  # Can't change argument names in the functions pytest expects
-"tests/doc/test_rst.py" = ["ARG"]  # For the lightning example
 
 [tool.ruff.lint.flake8-annotations]
 suppress-dummy-args = true