Docs: sudo is required on the apt-key add not on wget (#18180)

Running the command as given in the current doc throws the error:

```
sudo wget -q -O - https://packages.grafana.com/gpg.key | apt-key add -
ERROR: This command can only be used by root.
```

The proposed change fixes this issue.

docs/sources/installation/debian.md

@@ -51,7 +51,7 @@ sudo add-apt-repository "deb https://packages.grafana.com/oss/deb beta main"
 Use the above line even if you are on Ubuntu or another Debian version. Then add our gpg key. This allows you to install signed packages.
 Use the above line even if you are on Ubuntu or another Debian version. Then add our gpg key. This allows you to install signed packages.
 
 
 ```bash
 ```bash
-sudo wget -q -O - https://packages.grafana.com/gpg.key | apt-key add -
+wget -q -O - https://packages.grafana.com/gpg.key | sudo apt-key add -
 ```
 ```
 
 
 Update your Apt repositories and install Grafana
 Update your Apt repositories and install Grafana