Remove GitHub workflow

- GitHub is refusing to allow an integration to create .github/main.workflow and Flux is unable to push the sync git tag to the repo

.github/main.workflow

@@ -1,21 +0,0 @@
-workflow "Validate manifests" {
-  on = "push"
-  resolves = ["helm-lint"]
-}
-
-action "yaml-lint" {
-  uses = "stefanprodan/gh-actions/yamllint@master"
-  args = ["-d '{extends: relaxed, rules: {line-length: {max: 120}}}' -f parsable ./releases/*"]
-}
-
-action "kube-lint" {
-  needs = ["yaml-lint"]
-  uses = "stefanprodan/gh-actions/kubeval@master"
-  args = "workloads/*"
-}
-
-action "helm-lint" {
-  needs = ["kube-lint"]
-  uses = "stefanprodan/gh-actions/helm@master"
-  args = ["lint charts/*"]
-}