Correct ssh-copy-id command syntax

The ssh-copy-id command syntax in sdk-ade-remote-debugging.yaml is
incorrect in two ways:

- The user is in capitals, whilst the actual username used should be in
  lower case
- The test case uses `$HOST` as a convention for the hostname/IP to be used
  for the target device, this command is missing the dollar sign.

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

test-cases/sdk-ade-remote-debugging.yaml

@@ -41,7 +41,7 @@ run:
     - $ ade sysroot install
     - "Enable key-based SSH login on the target device"
     - $ ssh-keygen -t rsa -m PEM
-    - $ ssh-copy-id USER@HOST
+    - $ ssh-copy-id user@$HOST
     - "Clone the source code for the HelloWorld sample agent on the SDK host"
     - $ git clone https://gitlab.apertis.org/sample-applications/helloworld-simple-agent
     - $ cd helloworld-simple-agent