docs: remove duplicate skills toctree entry

Signed-off-by: Chen Cui <chcui@nvidia.com>

Author: cuichenx

docs/skills-index.md

@@ -61,7 +61,6 @@ skills/nemo-mbridge-perf-activation-recompute/SKILL
 skills/nemo-mbridge-recipe-recommender/references/recipe-index
 skills/nemo-mbridge-perf-nsys-analysis/references/pitfalls
 skills/nemo-mbridge-perf-nsys-analysis/references/sql-recipes
-skills/nemo-mbridge-recipe-recommender/references/recipe-index
 ```
 
 ```{toctree}