Use sticky comments for README Diff

[WyriHaximus]

After filing LouisBrunner/diff-action#21 this was addressed in LouisBrunner/diff-action#22 and released in https://github.com/LouisBrunner/diff-action/releases/tag/v2.1.0

[github-actions]

Smart Diff (cron-jobs): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/cron-jobs/README.current.md
+++ charts/cron-jobs/README.md

[github-actions]

Smart Diff (docker-hub-exporter): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/docker-hub-exporter/README.current.md
+++ charts/docker-hub-exporter/README.md

[github-actions]

Smart Diff (redirect): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/redirect/README.current.md
+++ charts/redirect/README.md

[github-actions]

Smart Diff (pi-hole-exporter): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/pi-hole-exporter/README.current.md
+++ charts/pi-hole-exporter/README.md

[github-actions]

Smart Diff (redis-db-assignment-operator): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/redis-db-assignment-operator/README.current.md
+++ charts/redis-db-assignment-operator/README.md

[github-actions]

Smart Diff (default-backend): Success

Check succeeded with tolerance same (expected same or better)

===================================================================
--- charts/default-backend/README.current.md
+++ charts/default-backend/README.md