Fix POSIX compliance: change == to = in send-heartbeat

Co-authored-by: gsanchietti <804596+gsanchietti@users.noreply.github.com>

Author: Copilot

packages/ns-plug/files/send-heartbeat

@@ -23,7 +23,7 @@ fi
 
 # Temporary send data to new endpoint
 # To be removed when the migration to new my.nethesis.it will be completed
-if [ "$TYPE" == "enterprise" ]; then
+if [ "$TYPE" = "enterprise" ]; then
     /usr/bin/curl -m 180 --retry 3 -L -s -X POST \
        --user "$SYSTEM_ID:$SYSTEM_SECRET" https://my.nethesis.it/proxy/heartbeat >/dev/null
     exit 0