fix(helm): update chart thanos to 15.7.26 (#7313)

| datasource | package | from    | to      |
| ---------- | ------- | ------- | ------- |
| helm       | thanos  | 15.7.25 | 15.7.26 |

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

kubernetes/main/apps/monitoring/thanos/app/helmrelease.yaml

@@ -10,7 +10,7 @@ spec:
   chart:
     spec:
       chart: thanos
-      version: 15.7.25
+      version: 15.7.26
       sourceRef:
         kind: HelmRepository
         name: bitnami-charts