Update indexed-gzip requirement from <=1.9.1 to <=1.9.4

Updates the requirements on [indexed-gzip](https://github.com/pauldmccarthy/indexed_gzip) to permit the latest version.
- [Release notes](https://github.com/pauldmccarthy/indexed_gzip/releases)
- [Changelog](https://github.com/pauldmccarthy/indexed_gzip/blob/main/CHANGELOG.md)
- [Commits](pauldmccarthy/indexed_gzip@v0.1...v1.9.4)

---
updated-dependencies:
- dependency-name: indexed-gzip
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -20,7 +20,7 @@ dependencies = [
     'importlib_resources; python_version < "3.11"',
     "acres",
     "fmriprep >= 24.1.0, <= 24.1.1",
-    "indexed_gzip <= 1.9.1",
+    "indexed_gzip <= 1.9.4",
     "looseversion",
     "networkx ~= 3.3",  # nipype needs networkx, but 3+ isn"t compatible with nipype 1.8.5
     "nibabel <= 5.3.2",