docs: added code blocks without headers (#2560)

docs/content/usage/create-medusa-app.mdx

@@ -44,7 +44,7 @@ You’ll then be asked to enter the name of the directory you want the project t
 
 Next, you’ll be asked to choose the Medusa starter used to install the Medusa server. You can either pick the default Medusa starter, the Contentful starter or enter a starter URL by choosing `Other`:
 
-```bash
+```bash noHeader
 ? Which Medusa starter would you like to install? …
 ❯ medusa-starter-default
   medusa-starter-contentful
@@ -63,7 +63,7 @@ You can learn more about the Contentful starter in the [Contentful Integration d
 
 After choosing the Medusa starter, you’ll be asked to choose the storefront starter. You can choose one of the starters in the list included or choose `None` to skip installing a storefront:
 
-```bash
+```bash noHeader
 ? Which storefront starter would you like to install?
 ❯ Gatsby Starter
 Next.js Starter
@@ -85,7 +85,7 @@ Learn more about the [Next.js](../starters/nextjs-medusa-starter.md) and [Gatsby
 
 After choosing the above starters, the installation of each component will begin along with its dependencies. Once the installation is done, you’ll see instructions related to how to start each component.
 
-```bash
+```bash noHeader
 Your project is ready. The available commands are:
 
 Medusa API
@@ -107,7 +107,7 @@ The commands will differ based on your choices in previous prompts.
 
 Inside the root project directory which was specified at the beginning of the installation process you’ll find the following directory structure:
 
-```bash
+```bash noHeader
 /my-medusa-store
   /storefront // Medusa storefront starter
   /backend // Medusa starter as a backend option