chore: bump pydata-sphinx-theme from 0.15.2 to 0.15.4 in the pip group (pyOpenSci#414)

Bumps the pip group with 1 update: [pydata-sphinx-theme](https://github.com/pydata/pydata-sphinx-theme).


Updates `pydata-sphinx-theme` from 0.15.2 to 0.15.4
- [Release notes](https://github.com/pydata/pydata-sphinx-theme/releases)
- [Changelog](https://github.com/pydata/pydata-sphinx-theme/blob/main/RELEASE.md)
- [Commits](pydata/pydata-sphinx-theme@v0.15.2...v0.15.4)

---
updated-dependencies:
- dependency-name: pydata-sphinx-theme
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: pip
...

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

Author: dependabot[bot]

pyproject.toml

@@ -8,7 +8,7 @@ dynamic = [
     "version"
 ]
 dependencies = [
-    "pydata-sphinx-theme==0.15.2",
+    "pydata-sphinx-theme==0.15.4",
     "myst-nb",
     "sphinx",
     "sphinx-autobuild",