Remove sections that just point to packaging guide

There are two sections that indirectly point to the packaging guide.
Remove these as they don't really add anything.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

content/guides/gitlab-based_packaging_workflow.md

@@ -134,14 +134,3 @@ shipped in `debian/patches` folder.
 To make working with those patches a bit easier for those used to `git rebase`,
 [the `gbp pq` tool provides a way to convert patches to git branches and
 back](https://honk.sigxcpu.org/projects/git-buildpackage/manual-html/gbp.patches.html).
-
-# How to issue a release
-
-The process for landing downstream changes is documented in the
-[ci-package-builder documentation]({{< ref "apertis_packaging_guide.md#landing-downstream-changes-to-the-main-archive" >}}).
-
-# How to add a new packaging repository
-
-The process for adding new packages from Debian is documented in the
-[ci-package-builder documentation]({{< ref "apertis_packaging_guide.md#adding-new-packages-from-debian" >}}).
-