remove content which has moved to f/website

docs/_files/cluster-dashboard.png

docs/_files/commit-status-flow.png

docs/_files/commit-status-github-failure.png

docs/_files/commit-status-github-overview.png

docs/_files/commit-status-github-success.png

docs/_files/commit-status-gitlab-failure.png

docs/_files/commit-status-gitlab-success.png

docs/_files/cp-dashboard-p1.png

docs/_files/cp-dashboard-p2.png

docs/_files/flux-icon.svg

docs/_files/flux-icon@2x.png

docs/_files/helm-controller-alerts.png

docs/_files/helm-controller.png

docs/_files/image-update-automation.png

docs/_files/kustomize-controller.png

docs/_files/notification-controller.png

docs/_files/slack-error-alert.png

docs/_files/slack-info-alert.png

docs/_files/source-controller.png

docs/_files/toolkit-icon.png