.github: delete the unused renovate config

Self-hosted-runner shape (repositories, platform, gitAuthor) that a
repo-level config cannot set, and nothing has run it since the workflow
was removed in 6a311f4ab.

.github/CODEOWNERS

@@ -7,4 +7,3 @@ Dockerfile* @ohdearaugustin @nblock
 .goreleaser.yaml @ohdearaugustin @nblock
 /docs/ @ohdearaugustin @nblock
 /.github/workflows/ @ohdearaugustin @nblock
-/.github/renovate.json @ohdearaugustin @nblock

.github/renovate.json

@@ -1,34 +0,0 @@
-{
-  "baseBranches": ["main"],
-  "username": "renovate-release",
-  "gitAuthor": "Renovate Bot <bot@renovateapp.com>",
-  "branchPrefix": "renovateaction/",
-  "onboarding": false,
-  "extends": ["config:base", ":rebaseStalePrs"],
-  "ignorePresets": [":prHourlyLimit2"],
-  "enabledManagers": ["dockerfile", "gomod", "github-actions", "regex"],
-  "includeForks": true,
-  "repositories": ["juanfont/headscale"],
-  "platform": "github",
-  "packageRules": [
-    {
-      "matchDatasources": ["go"],
-      "groupName": "Go modules",
-      "groupSlug": "gomod",
-      "separateMajorMinor": false
-    },
-    {
-      "matchDatasources": ["docker"],
-      "groupName": "Dockerfiles",
-      "groupSlug": "dockerfiles"
-    }
-  ],
-  "regexManagers": [
-    {
-      "fileMatch": [".github/workflows/.*.yml$"],
-      "matchStrings": ["\\s*go-version:\\s*\"?(?<currentValue>.*?)\"?\\n"],
-      "datasourceTemplate": "golang-version",
-      "depNameTemplate": "actions/go-version"
-    }
-  ]
-}