fix the banner image

Author: HarshCasper

README.md

@@ -1,5 +1,5 @@
 <p align="center">
-  <img src="https://raw.githubusercontent.com/localstack/localstack/master/doc/localstack-readme-banner.svg" alt="LocalStack - A fully functional local cloud stack">
+  <img src="https://raw.githubusercontent.com/localstack/localstack/master/docs/localstack-readme-banner.svg" alt="LocalStack - A fully functional local cloud stack">
 </p>
 <p align="center">  
   <a href="https://localstack.cloud/slack">