Remove orphaned build page and navigation code

The build page was removed from navigation but the file and associated
navigation highlighting code remained. Clean up by removing both.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: James R. Perkins <jperkins@ibm.com>

Author: jamezp

content/build.html

@@ -147,8 +147,6 @@
         item.classList.add('current');
       } else if (section === 'blogs' && (currentPath.startsWith('/blogs') || currentPath.startsWith('/posts'))) {
         item.classList.add('current');
-      } else if (section === 'build' && currentPath.startsWith('/build')) {
-        item.classList.add('current');
       }
     });
   });