ci(dependabot): update helm template images (#12301)

## Motivation

Closes #7657

## Implementation information

Switch to `directories` and search recursively for any charts.

Signed-off-by: Mike Beaumont <mjboamail@gmail.com>

.github/dependabot.yml

@@ -22,15 +22,10 @@ updates:
       - dependency-name: github.com/envoyproxy/go-control-plane
 
   - package-ecosystem: "docker"
-    directory: "/tools/releases/dockerfiles"
-    schedule:
-      interval: "weekly"
-    open-pull-requests-limit: 15
-    labels:
-      - "dependencies"
-
-  - package-ecosystem: "docker"
-    directory: "/test/dockerfiles"
+    directories:
+      - "/tools/releases/dockerfiles"
+      - "/test/dockerfiles"
+      - "/deployments/charts/**/*"
     schedule:
       interval: "weekly"
     open-pull-requests-limit: 15