docs(tenets): update Idiomatic tenet to Progressive (#823)

docs/index.md

@@ -17,7 +17,7 @@ This project separates core utilities that will be available in other runtimes v
 * **Keep it lean**. Additional dependencies are carefully considered for security and ease of maintenance, and prevent negatively impacting startup time.
 * **We strive for backwards compatibility**. New features and changes should keep backwards compatibility. If a breaking change cannot be avoided, the deprecation and migration process should be clearly defined.
 * **We work backwards from the community**. We aim to strike a balance of what would work best for 80% of customers. Emerging practices are considered and discussed via Requests for Comment (RFCs)
-* **Idiomatic**. Utilities follow programming language idioms and language-specific best practices.
+* **Progressive**. Utilities are designed to be incrementally adoptable for customers at any stage of their Serverless journey. They follow language idioms and their community’s common practices.
 
 ## Install