fix: fix broken markdown-link-check CI job after #2611 got merged (#2655)

Author: binarycat0

getting-started/keycloak/README.md

@@ -46,7 +46,7 @@ Polaris is configured with 3 realms:
   issued by both Polaris and Keycloak.
 
 For more information about how to configure Polaris with external authentication, see the
-[Polaris documentation](https://polaris.apache.org/in-dev/unreleased/external-idp/).
+[Polaris documentation](https://polaris.apache.org/in-dev/unreleased/managing-security/external-idp/).
 
 ## Starting the Example
 

site/content/in-dev/unreleased/managing-security/external-idp/keycloak-idp.md

@@ -48,7 +48,7 @@ Polaris is configured with 3 realms:
   issued by both Polaris and Keycloak.
 
 For more information about how to configure Polaris with external authentication, see the
-[Polaris documentation](https://polaris.apache.org/in-dev/unreleased/external-idp/).
+[Polaris documentation]({{% ref "../external-idp" %}}).
 
 ## Starting the Example