Update Intro_to_Mill_Header.adoc

docs/modules/ROOT/partials/Intro_to_Mill_Header.adoc

@@ -41,7 +41,7 @@ even as it grows from a small project to a large codebase or monorepo with hundr
   the logic necessary to build your project, while providing tools to let you identify
   and resolve bottlenecks in your build
 
-* *Beyond YAML and Bash*: Mill config and custom logic is written in
+* *Maintainability*: Mill goes beyond YAML and Bash, with config and custom logic written in
   xref:_custom_build_logic[concise type-checked code],
   rather than shell scripts, XML or YAML. This lets IDEs
   (xref:{language-small}lib/installation-ide.adoc#_intellij[IntelliJ] or