chore(deps-dev): bump pytest-doctestplus from 1.4.0 to 1.6.0

Bumps [pytest-doctestplus](https://github.com/scientific-python/pytest-doctestplus) from 1.4.0 to 1.6.0.
- [Release notes](https://github.com/scientific-python/pytest-doctestplus/releases)
- [Changelog](https://github.com/scientific-python/pytest-doctestplus/blob/main/CHANGES.rst)
- [Commits](scientific-python/pytest-doctestplus@v1.4.0...v1.6.0)

---
updated-dependencies:
- dependency-name: pytest-doctestplus
  dependency-version: 1.6.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -68,7 +68,7 @@ test = [
     "pytest-cases ==3.9.1",
     "pytest-custom_exit_code ==0.3.0",
     "pytest-cov ==6.3.0",  # Uses: coverage[toml] >=7.5
-    "pytest-doctestplus ==1.4.0",
+    "pytest-doctestplus ==1.6.0",
     "pytest-env ==1.2.0",
 ]