Update src/javascript-node/README.md

Co-authored-by: Samruddhi Khandale <skhandale@microsoft.com>

Author: chrmarti

src/javascript-node/README.md

@@ -19,7 +19,7 @@
 
 See **[history](history)** for information on the contents of published images.
 
-## Using this definition
+## Using this image
 
 While the definition itself works unmodified, you can select the version of Node.js the container uses by updating the `VARIANT` arg in the included `devcontainer.json` (and rebuilding if you've already created the container).