use armored ascii key instead of .gpg

Author: LLdaniel

content/manuals/engine/install/debian.md

@@ -120,7 +120,7 @@ Docker from the repository.
    URIs: https://download.docker.com/linux/debian/\n\
    Suites: $(. /etc/os-release && echo "$VERSION_CODENAME")\n\
    Components: stable\n\
-   Signed-By: /etc/apt/keyrings/docker.gpg" | \
+   Signed-By: /etc/apt/keyrings/docker.asc" | \
    sudo tee /etc/apt/sources.list.d/docker.sources > /dev/null
 
    sudo apt-get update