fix: pin docker-registry haSharedSecret to avoid sandbox manifest churn (#7108)

The docker-registry Helm subchart generates a random haSharedSecret on
every helm template run when the value is not set. This causes
complete.yaml and dev.yaml to always show as modified after running
`make sandbox-build`, even with no actual deployment changes.

Pin the secret to a static value in flyte-sandbox values.yaml since this
is a local development sandbox environment.

Signed-off-by: Kevin Su <pingsutw@apache.org>

Author: pingsutw

charts/flyte-sandbox/values.yaml

@@ -5,6 +5,8 @@ docker-registry:
     pullPolicy: Never
   persistence:
     enabled: false
+  secrets:
+    haSharedSecret: flytesandboxsecret
   service:
     type: NodePort
     nodePort: 30000

docker/sandbox-bundled/manifests/complete.yaml

@@ -1112,7 +1112,7 @@ type: Opaque
 ---
 apiVersion: v1
 data:
-  haSharedSecret: dk8yMDZDOTR6SHRrQUNrUQ==
+  haSharedSecret: Zmx5dGVzYW5kYm94c2VjcmV0
   proxyPassword: ""
   proxyUsername: ""
 kind: Secret
@@ -1707,7 +1707,7 @@ spec:
     metadata:
       annotations:
         checksum/config: 8f50e768255a87f078ba8b9879a0c174c3e045ffb46ac8723d2eedbe293c8d81
-        checksum/secret: cf1faf39f000efb8810269147692898bc61a92952ded23c8145cc963dc8ca1b3
+        checksum/secret: 829c19e3c86dcb9b7d4c44e6a73463c6a6467d824200e87e2d7999f70dc0f5f9
       labels:
         app: docker-registry
         release: flyte-sandbox

docker/sandbox-bundled/manifests/dev.yaml

@@ -826,7 +826,7 @@ metadata:
 ---
 apiVersion: v1
 data:
-  haSharedSecret: eXNVaWVTRkFhdHNsS3V3RQ==
+  haSharedSecret: Zmx5dGVzYW5kYm94c2VjcmV0
   proxyPassword: ""
   proxyUsername: ""
 kind: Secret
@@ -1323,7 +1323,7 @@ spec:
     metadata:
       annotations:
         checksum/config: 8f50e768255a87f078ba8b9879a0c174c3e045ffb46ac8723d2eedbe293c8d81
-        checksum/secret: a9f352bd07e84295ab41efa4e840927a884c894cab47f8a95c19e6e90393baaf
+        checksum/secret: 829c19e3c86dcb9b7d4c44e6a73463c6a6467d824200e87e2d7999f70dc0f5f9
       labels:
         app: docker-registry
         release: flyte-sandbox