Fix typo.

Author: prada-b

docs/index.md

@@ -17,6 +17,6 @@ trustworthy, ethical, and secure. These models should have a few desired
 properties, such as robustness and interpretability, such that humans can
 easily understand the generated information. This would mean designing agents
 that are expected to learn desirable behavior with minimal supervision and data
-data that are provably stable and generalize to unseen distribution. We believe
+that are provably stable and generalize to unseen distribution. We believe
 these objectives can be stably achieved by designing knowledge-guided,
 neuro-symbolic agents.