Dex pods fail on kubernetes version 1.21.3

Dex pod is crashing due to a recent kubernetes upversioning to 1.21.3.
This causes oidc-auth-apps to fail to apply. This commit implements
the fix suggested for it upstream:
https://github.com/dexidp/dex/issues/2082#issuecomment-818124478

Test Plan:
PASS: apply oidc-auth-apps on kubernetes version 1.18.1
PASS: apply oidc-auth-apps on kubernetes version 1.19.13
PASS: apply oidc-auth-apps on kubernetes version 1.20.9
PASS: apply oidc-auth-apps on kubernetes version 1.21.3

Change-Id: Ide9376820647fb46dfd27ea56623dfeefce9f4dd
Closes-Bug: 1948981
Signed-off-by: Jerry Sun <jerry.sun@windriver.com>

stx-oidc-auth-helm/stx-oidc-auth-helm/manifests/manifest.yaml

@@ -23,6 +23,11 @@ data:
   values:
     image: docker.io/starlingx/dex
     imageTag: stx.4.0-v2.14.0-1
+    env:
+      - name: KUBERNETES_POD_NAMESPACE
+        valueFrom:
+          fieldRef:
+            fieldPath: metadata.namespace
     config:
       enablePasswordDB: false
       web: