Fix the doc of resting_heart_rate

[gcappon]

It is:
{
"status": "success",
"code": 200,
"message": "Request successful.",
"data": {
"date": "2023-05-15",
"data": {
"time": "00:00:00",
"value": 56.01,
"error": 10.73
}
}
}

not

{
"status": "success",
"code": 200,
"message": "Request successful.",
"data": {
"date": "2023-05-15",
"data": [{
"time": "00:00:00",
"value": 56.01,
"error": 10.73
}]
}
}