Improve Clarity and Structure of Faithfulness Explanation in Documentation (#1114)

## Description
This PR enhances the documentation by improving the clarity and
structure of the faithfulness explanation. The changes include:

- Reorganizing the content for better flow and readability
- Clarifying the process of determining the faithfulness of generated
answers
- Fixing grammatical errors and improving sentence structure

Author: aybruhm

docs/concepts/metrics/faithfulness.md

@@ -2,7 +2,7 @@
 
 This measures the factual consistency of the generated answer against the given context. It is calculated from answer and retrieved context. The answer is scaled to (0,1) range. Higher the better.
 
-The generated answer is regarded as faithful if all the claims that are made in the answer can be inferred from the given context. To calculate this a set of claims from the generated answer is first identified. Then each one of these claims are cross checked with given context to determine if it can be inferred from given context or not. The faithfulness score is given by divided by
+The generated answer is regarded as faithful if all the claims made in the answer can be inferred from the given context. To calculate this, a set of claims from the generated answer is first identified. Then each of these claims is cross-checked with the given context to determine if it can be inferred from the context. The faithfulness score is given by:
 
 ```{math}
 :label: faithfulness