fixed verb agreement @ available_metrics (#1574)

Author: gabrielhomsi

docs/concepts/metrics/available_metrics/index.md

@@ -2,7 +2,7 @@
 
 Ragas provides a set of evaluation metrics that can be used to measure the performance of your LLM application. These metrics are designed to help you objectively measure the performance of your application. Metrics are available for different applications and tasks, such as RAG and Agentic workflows. 
 
-Each metric are essentially paradigms that is designed to evaluate a particular aspect of the application. LLM Based metrics might use one or more LLM calls to arrive at the score or result. One can also modify or write your own metrics using ragas.
+Each metric are essentially paradigms that are designed to evaluate a particular aspect of the application. LLM Based metrics might use one or more LLM calls to arrive at the score or result. One can also modify or write your own metrics using ragas.
 
 ## Retrieval Augmented Generation
 - [Context Precision](context_precision.md)