ops-dashboard: revert oauth2-proxy back to v7.18.0

v8 has a regression where it always deploys redis, even when it's disabled.
Issue: oauth2-proxy/manifests#350

Author: BacLuc

.ops/ops-dashboard/Chart.lock

@@ -1,15 +1,15 @@
 dependencies:
 - name: oauth2-proxy
   repository: https://oauth2-proxy.github.io/manifests
-  version: 8.2.0
+  version: 7.18.0
 - name: kubernetes-dashboard
   repository: https://kubernetes.github.io/dashboard/
   version: 7.13.0
 - name: oauth2-proxy
   repository: https://oauth2-proxy.github.io/manifests
-  version: 8.2.0
+  version: 7.18.0
 - name: oauth2-proxy
   repository: https://oauth2-proxy.github.io/manifests
-  version: 8.2.0
-digest: sha256:142da8fd57bc6a24ca609e3ad8a4dfb1cca54f5fda7972dea16ad14477d3dcec
-generated: "2025-08-24T16:31:56.7842085Z"
+  version: 7.18.0
+digest: sha256:d119e0b8ffb14fc7aee209549ea98ee92c80eefe64a20f4b48a5a7b193efc9c6
+generated: "2025-08-14T11:03:55.532011762Z"

.ops/ops-dashboard/Chart.yaml

@@ -26,16 +26,16 @@ appVersion: 0.1.0
 dependencies:
   - name: oauth2-proxy
     alias: grafana-proxy
-    version: 8.2.0
+    version: 7.18.0
     repository: https://oauth2-proxy.github.io/manifests
   - name: kubernetes-dashboard
     version: 7.13.0
     repository: https://kubernetes.github.io/dashboard/
   - name: oauth2-proxy
     alias: kubernetes-dashboard-proxy
-    version: 8.2.0
+    version: 7.18.0
     repository: https://oauth2-proxy.github.io/manifests
   - name: oauth2-proxy
     alias: logging-proxy
-    version: 8.2.0
+    version: 7.18.0
     repository: https://oauth2-proxy.github.io/manifests