Fix documentation links to Alpha versiond definition

doc/user/discussions/index.md

@@ -497,7 +497,7 @@ introduced by [#25381](https://gitlab.com/gitlab-org/gitlab/-/issues/25381).
 
 ### Batch Suggestions
 
-> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/25486) in GitLab 13.1 as an [alpha feature](https://about.gitlab.com/handbook/product/#alpha).
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/25486) in GitLab 13.1 as an [alpha feature](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha).
 > - It was deployed behind a feature flag, disabled by default.
 > - [Became enabled by default](https://gitlab.com/gitlab-org/gitlab/-/issues/227799) on GitLab 13.2.
 > - It's enabled on GitLab.com.

doc/user/profile/preferences.md

@@ -45,7 +45,7 @@ The default theme is Indigo. You can choose between 10 themes:
 
 GitLab has started work on dark mode! The dark mode Alpha release is available in the
 spirit of iteration and the lower expectations of
-[Alpha versions](https://about.gitlab.com/handbook/product/#alpha).
+[Alpha versions](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha).
 
 Progress on dark mode is tracked in the [Dark theme epic](https://gitlab.com/groups/gitlab-org/-/epics/2902). See the epic for:
 

doc/user/project/clusters/serverless/index.md

@@ -9,7 +9,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 > Introduced in GitLab 11.5.
 
 WARNING:
-Serverless is currently in [alpha](https://about.gitlab.com/handbook/product/#alpha).
+Serverless is currently in [alpha](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha).
 
 ## Overview