Revert "feat(skills): integrate NVIDIA/skills as a trusted skills hub tap"

This reverts commit 9992e32db3.

tools/skills_hub.py

@@ -401,14 +401,6 @@ class GitHubSource(SkillSource):
         {"repo": "openai/skills", "path": "skills/.system/"},
         {"repo": "anthropics/skills", "path": "skills/"},
         {"repo": "huggingface/skills", "path": "skills/"},
-        # NVIDIA/skills: NVIDIA-verified skills for CUDA-X, AIQ, cuOpt,
-        # cuPyNumeric, DeepStream, NeMo, NemoClaw, etc. Each skill ships
-        # alongside a signed `skill.oms.sig`, an OMS-signed `skill-card.md`
-        # (governance card), and an `evals/` directory — synced daily from
-        # the NVIDIA product repos. Treated as `trusted` (see
-        # `tools/skills_guard.py::TRUSTED_REPOS`). Sample layout:
-        # https://github.com/NVIDIA/skills/tree/main/skills
-        {"repo": "NVIDIA/skills", "path": "skills/"},
         {"repo": "garrytan/gstack", "path": ""},
     ]