host_monitor_app: Updating checkpoint name of S0 and S5

Update the name to meet the requirement.

Tested:
```
bmc$ busctl call --verbose com.google.gbmc.boot_time_monitor /xyz/openbmc_project/time/boot/host0 xyz.openbmc_project.Time.Boot.Checkpoint GetCheckpointList
MESSAGE "a(sxx)" {
        ARRAY "(sxx)" {

                STRUCT "sxx" {
                        STRING "To_Off";
                        INT64 1704350090260;
                        INT64 2211580;
                };
                STRUCT "sxx" {
                        STRING "Off";
                        INT64 1704350098511;
                        INT64 2219830;
                };
        };
};

```

Google-Bug-Id: 296787899
Google-Bug-Id: 296791279
Change-Id: Ie50d302d3b3e851a8c4db09eab7acc1cf5718bb3
Signed-off-by: Michael Shen <gpgpgp@google.com>
diff --git a/src/host_monitor_app.cpp b/src/host_monitor_app.cpp
index 9440c12..45a0978 100644
--- a/src/host_monitor_app.cpp
+++ b/src/host_monitor_app.cpp
@@ -70,8 +70,8 @@
         sdbusplus::bus::match::rules::propertiesChanged(kHostPath.data(),
                                                         kHostIface.data()),
         [this](sdbusplus::message::message& message) {
-        constexpr std::string_view kS0 = "S0";
-        constexpr std::string_view kS5 = "S5";
+        constexpr std::string_view kS0 = "Off";
+        constexpr std::string_view kS5 = "To_Off";
 
         std::string objectName;
         boost::container::flat_map<