Make text agree example API version

Update the text to match the example.  Be explicit about
which API version we support.

Signed-off-by: Aidan Delaney <[email protected]>

> _By signing off you acknowledge adhering to the requirements listed here: https://probot.github.io/apps/dco/_

Signed-off-by: Aidan Delaney <[email protected]>

Author: AidanDelaney

content/docs/app-developer-guide/using-inline-buildpacks.md

@@ -26,7 +26,7 @@ id = "me/rake-tasks"
   inline = "rake package"
 ```
 
-In this example, the `me/rake-tasks` inline buildpack is configured to run after the `example/ruby` buildpack. The inline script is compatible with API version `0.4` (this is a required field), and it will execute the `rake package` command during the build step.
+In this example, the `me/rake-tasks` inline buildpack is configured to run after the `example/ruby` buildpack. The inline script is compatible with buildpack API version `0.6` (this is a required field), and it will execute the `rake package` command during the build step.
 
 > **Note:** Inline buildpacks will _always_ pass detection.