fix broken url in docs\source\index.mdx (#1813)

docs/source/index.mdx

@@ -21,7 +21,7 @@ Check the appropriate sections of the documentation depending on your needs:
 - [`PPOTrainer`](ppo_trainer): *Further fine-tune the supervised fine-tuned model using PPO algorithm*
 - [Best-of-N Sampling](best-of-n): *Use best of n sampling as an alternative way to sample predictions from your active model*
 - [`DPOTrainer`](dpo_trainer): *Direct Preference Optimization training using `DPOTrainer`.*
-- [`TextEnvironment`](text_environment): *Text environment to train your model using tools with RL.*
+- [`TextEnvironment`](text_environments): *Text environment to train your model using tools with RL.*
 
 ## Examples