add namespace environment variable back

Signed-off-by: Chengwei Guo <chengweiguo@bytedance.com>

Author: cw-Guo

config/manager/manager.yaml

@@ -48,6 +48,12 @@ spec:
             port: 8081
           initialDelaySeconds: 5
           periodSeconds: 10
+        env:
+          - name: NAMESPACE
+            valueFrom:
+              fieldRef:
+                apiVersion: v1
+                fieldPath: metadata.namespace
         resources:
           limits:
             cpu: 200m