sensor-mon: Fix unused lambda capture warning

Fix:
```
../sensor-monitor/threshold_alarm_logger.cpp:135:39: error: lambda capture 'this' is not used [-Werror,-Wunused-lambda-capture]
  135 |                           [interface, this](const auto& object) {
```

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I47d5e772f5aef624f53959a98268857ac04660c5
diff --git a/sensor-monitor/threshold_alarm_logger.cpp b/sensor-monitor/threshold_alarm_logger.cpp
index 6316dad..646b1fe 100644
--- a/sensor-monitor/threshold_alarm_logger.cpp
+++ b/sensor-monitor/threshold_alarm_logger.cpp
@@ -136,7 +136,7 @@
                               const auto& path = object.first;
                               const auto& service =
                                   object.second.begin()->first;
-                              checkThresholds(interface, path, service);
+                              this->checkThresholds(interface, path, service);
                           });
         });
 }