Bump certifi in /examples/xr-transformer-neurips21

Bumps [certifi](https://github.com/certifi/python-certifi) from 2021.5.30 to 2023.7.22.
- [Commits](certifi/python-certifi@2021.05.30...2023.07.22)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: direct:production
...

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

examples/xr-transformer-neurips21/requirements.txt

@@ -1,4 +1,4 @@
-certifi==2021.5.30
+certifi==2023.7.22
 charset-normalizer==2.0.6
 click==8.0.1
 docopt==0.6.2