chore(deps)(deps): update sphinx-book-theme requirement from >=1.0.1 to >=1.2.0 (#826)

chore(deps)(deps): update sphinx-book-theme requirement

Updates the requirements on [sphinx-book-theme](https://github.com/executablebooks/sphinx-book-theme) to permit the latest version.
- [Release notes](https://github.com/executablebooks/sphinx-book-theme/releases)
- [Changelog](https://github.com/executablebooks/sphinx-book-theme/blob/main/CHANGELOG.md)
- [Commits](executablebooks/sphinx-book-theme@v1.0.1...v1.2.0)

---
updated-dependencies:
- dependency-name: sphinx-book-theme
  dependency-version: 1.2.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements-doc.txt

@@ -10,7 +10,7 @@ sphinx>=5, <9.1.0
 myst-nb
 sphinx_thebe
 sphinx-autodoc-typehints
-sphinx-book-theme>=1.0.1
+sphinx-book-theme>=1.2.0
 sphinx-copybutton>=0.5.0
 sphinx-remove-toctrees
 jupyter-sphinx>=0.5.3