[MNT] [Dependabot](deps): Update sphinx-issues requirement

Updates the requirements on [sphinx-issues](https://github.com/sloria/sphinx-issues) to permit the latest version.
- [Commits](sloria/sphinx-issues@0.1.0...5.0.0)

---
updated-dependencies:
- dependency-name: sphinx-issues
  dependency-type: direct:production
...

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

pyproject.toml

@@ -71,7 +71,7 @@ docs = [
     "nbsphinx>=0.8.6",
     "numpydoc",
     "pydata-sphinx-theme",
-    "sphinx-issues<5.0.0",
+    "sphinx-issues<6.0.0",
     "sphinx-gallery<0.19.0",
     "sphinx-panels",
     "sphinx-design<0.7.0",