Use relative anchor link since this is the same file [ci skip]

Author: zzak

guides/source/active_storage_overview.md

@@ -540,7 +540,7 @@ Active Storage supports two ways to serve files: redirecting and proxying.
 WARNING: All Active Storage controllers are publicly accessible by default. The
 generated URLs are hard to guess, but permanent by design. If your files
 require a higher level of protection consider implementing
-[Authenticated Controllers](active_storage_overview.html#authenticated-controllers).
+[Authenticated Controllers](#authenticated-controllers).
 
 ### Redirect mode