ci: escape registry vars inside remote deploy heredoc

Same $$ fix as tracker for docker login on the Pi.

.drone.yml

@@ -176,8 +176,8 @@ steps:
         set -euo pipefail
         cd /opt/iled-shop
         git fetch origin
-        git checkout "${DRONE_COMMIT_SHA}"
-        echo "${REGISTRY_PASSWORD}" | docker login registry.zea.lt -u "${REGISTRY_USERNAME}" --password-stdin
+        git checkout "$${DRONE_COMMIT_SHA}"
+        echo "$${REGISTRY_PASSWORD}" | docker login registry.zea.lt -u "$${REGISTRY_USERNAME}" --password-stdin
         cd docker
         docker compose pull
         docker compose up -d --remove-orphans