[Metrics UI] Fix removing warning threshold from alert expressions (#93338)

Author: Zacqary

x-pack/plugins/infra/public/alerting/inventory/components/expression.tsx

@@ -137,7 +137,7 @@ export const Expressions: React.FC<Props> = (props) => {
   const updateParams = useCallback(
     (id, e: InventoryMetricConditions) => {
       const exp = alertParams.criteria ? alertParams.criteria.slice() : [];
-      exp[id] = { ...exp[id], ...e };
+      exp[id] = e;
       setAlertParams('criteria', exp);
     },
     [setAlertParams, alertParams.criteria]

x-pack/plugins/infra/public/alerting/metric_threshold/components/expression.tsx

@@ -98,7 +98,7 @@ export const Expressions: React.FC<Props> = (props) => {
   const updateParams = useCallback(
     (id, e: MetricExpression) => {
       const exp = alertParams.criteria ? alertParams.criteria.slice() : [];
-      exp[id] = { ...exp[id], ...e };
+      exp[id] = e;
       setAlertParams('criteria', exp);
     },
     [setAlertParams, alertParams.criteria]