Bump sphinx from 5.3 to 7.2.6 (#387)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.3 to 7.2.6.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v5.3.0...v7.2.6)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

website/requirements.txt

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) Contributors to the OpenEXR Project.
 
-sphinx == 5.3
+sphinx == 7.2.6
 breathe
 sphinx-press-theme