Update sphinx-copybutton requirement from ~=0.4.0 to ~=0.5.0 (#99)

Updates the requirements on [sphinx-copybutton](https://github.com/executablebooks/sphinx-copybutton) to permit the latest version.
- [Release notes](https://github.com/executablebooks/sphinx-copybutton/releases)
- [Changelog](https://github.com/executablebooks/sphinx-copybutton/blob/master/CHANGELOG.md)
- [Commits](executablebooks/sphinx-copybutton@v0.4.0...v0.5.0)

---
updated-dependencies:
- dependency-name: sphinx-copybutton
  dependency-type: direct:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements-dev.txt

@@ -13,5 +13,5 @@ pytest ~=6.2.5
 ipython ~=7.32.0
 numpydoc ~=1.2
 sphinx ~=4.3.2
-sphinx-copybutton ~=0.4.0
+sphinx-copybutton ~=0.5.0
 sphinx_rtd_theme ~=1.0.0