ci: digest-pin kubeconform docker image

Author: nicktrn

.github/workflows/helm-prerelease.yml

@@ -59,7 +59,7 @@ jobs:
             --output-dir ./helm-output
 
       - name: Validate manifests
-        uses: docker://ghcr.io/yannh/kubeconform:v0.7.0
+        uses: docker://ghcr.io/yannh/kubeconform:v0.7.0@sha256:85dbef6b4b312b99133decc9c6fc9495e9fc5f92293d4ff3b7e1b30f5611823c
         with:
           entrypoint: "/kubeconform"
           args: "-summary -output json ./helm-output"

.github/workflows/release-helm.yml

@@ -54,7 +54,7 @@ jobs:
             --output-dir ./helm-output
 
       - name: Validate manifests
-        uses: docker://ghcr.io/yannh/kubeconform:v0.7.0
+        uses: docker://ghcr.io/yannh/kubeconform:v0.7.0@sha256:85dbef6b4b312b99133decc9c6fc9495e9fc5f92293d4ff3b7e1b30f5611823c
         with:
           entrypoint: '/kubeconform'
           args: "-summary -output json ./helm-output"