metric-config: remove thresholds on total-memory

The total memory metric cannot change and it isn't really possible to
have a threshold on it.  Remove the bogus threshold.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I99659919afc55b636dc2a22dca33e0caae634847
diff --git a/health_metric_config.cpp b/health_metric_config.cpp
index 08ed3c3..6360203 100644
--- a/health_metric_config.cpp
+++ b/health_metric_config.cpp
@@ -219,14 +219,7 @@
     },
     "Memory": {
         "Frequency": 1,
-        "Window_size": 120,
-        "Threshold": {
-            "Critical_Upper": {
-                "Value": 85.0,
-                "Log": true,
-                "Target": ""
-            }
-        }
+        "Window_size": 120
     },
     "Memory_Available": {
         "Frequency": 1,