chore(deps-dev): 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/master/CHANGELOG.md)
- [Commits](executablebooks/sphinx-book-theme@v0.0.39...v1.1.0)

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

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

pyproject.toml

@@ -50,7 +50,7 @@ dev = [
 ]
 docs = [
     "sphinx~=3.3.1",
-    "sphinx-book-theme~=0.0.39",
+    "sphinx-book-theme>=0.0.39,<1.2.0",
     "sphinx-autodoc-typehints~=1.11.1",
     "sphinx-copybutton~=0.3.1",
 ]