Update what-is-defang.mdx

Change tagline to Develop Once, Deploy Anywhere

Author: Prakash-Sundaresan

docs/intro/what-is-defang.mdx

@@ -8,7 +8,7 @@ description: What is Defang?
 
 <iframe width="560" height="315" src="https://www.youtube.com/embed/afglsBYieuc?si=iKgUX4ejz7AixxqQ" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen style={{marginBottom: "2rem"}}></iframe>
 
-## Develop Anything, Deploy Anywhere.
+## Develop Once, Deploy Anywhere.
 
 Defang lets you take your app from Docker Compose to a secure and scalable deployment on your favorite cloud in minutes.