Update modus/app-manifest.mdx

Co-authored-by: Ryan Fox-Tyler <[email protected]>

Author: rderbier

modus/app-manifest.mdx

@@ -368,7 +368,7 @@ follow:
 MODUS_OPENAI_API_KEY="your openai key"
 ```
 
-You must exclude `.env` files from your source control. `modus new` does that
+You should exclude `.env` files from source control. Projects created with `modus new` exclude these files
 automatically for you when creating the project.
 
 ## Models