Merge pull request #45467 from xmudrii/install-keyrings

Add a note about /etc/apt/keyrings to pkgs.k8s.io migration guide

Author: k8s-ci-robot

content/en/blog/_posts/2023-08-15-pkgs-k8s-io-introduction.md

@@ -173,6 +173,8 @@ publishing packages to the Google-hosted repository in the future.
    curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.28/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
    ```
 
+_Update: In releases older than Debian 12 and Ubuntu 22.04, the folder `/etc/apt/keyrings` does not exist by default, and it should be created before the curl command._
+
 3. Update the `apt` package index:
 
    ```shell