docs: fix broken cross-references to regexes section in setup.md

Two links pointed to index.md#regexes-and-automated-builds, but the
'Regexes and automated builds' section lives in setup.md itself.
Use same-file anchors so the links resolve correctly.

Author: nielskaspers

content/manuals/docker-hub/repos/manage/builds/setup.md

@@ -170,15 +170,15 @@ You can configure your automated builds so that pushes to specific branches or t
     > [!NOTE]
     >
     > You can enter a name, or use a regex to match which source branch or tag
-    > names to build. To learn more, see [regexes](index.md#regexes-and-automated-builds).
+    > names to build. To learn more, see [regexes](#regexes-and-automated-builds).
 
 4. Enter the tag to apply to Docker images built from this source.
 
    > [!NOTE]
    >
    > If you configured a regex to select the source, you can reference the
    > capture groups and use its result as part of the tag. To learn more, see
-   > [regexes](index.md#regexes-and-automated-builds).
+   > [regexes](#regexes-and-automated-builds).
 
 5. Repeat steps 2 through 4 for each new build rule you set up.