remove non-deb822 format sources

Author: LLdaniel

content/manuals/engine/install/debian.md

@@ -114,13 +114,7 @@ Docker from the repository.
    sudo curl -fsSL {{% param "download-url-base" %}}/gpg -o /etc/apt/keyrings/docker.asc
    sudo chmod a+r /etc/apt/keyrings/docker.asc
 
-   # Add the repository to Apt sources (legacy format):
-   echo \
-     "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] {{% param "download-url-base" %}} \
-     $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
-     sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
-
-   # Add the repository to Apt sources (new deb822 format, introduced with Trixie):
+   # Add the repository to Apt sources:
    echo -e \
    "Types: deb\n\
    URIs: https://download.docker.com/linux/debian/\n\