sdk/docs: Bump versions for sphinx dependencies

Currently, the sphinx dependencies in `docs/add_requirements.txt` are
outdated, causing our CI pipeline to fail.

This bumps the versions for the additional requirements for the
compilation of the documentation to their newest working state.

Fixes eclipse-basyx#385

Author: s-heppner

sdk/docs/add-requirements.txt

@@ -1,4 +1,4 @@
 # Additional requirements for building the docs
-sphinx~=7.2
-sphinx-rtd-theme~=2.0
-sphinx-argparse~=0.4.0
+sphinx~=8.2
+sphinx-rtd-theme~=3.0
+sphinx-argparse~=0.5.0