ci: use static target: automation label in renovate config

The `target: automation` label is used by the Angular team to identify PRs that are created by automation. This is used to skip some checks that are not required for automated PRs.

Author: alan-agius4

renovate.json

@@ -4,14 +4,6 @@
   "extends": ["github>angular/dev-infra//renovate-presets/default.json5"],
   "ignorePaths": ["tests/legacy-cli/e2e/assets/**", "tests/schematics/update/packages/**"],
   "packageRules": [
-    {
-      "matchBaseBranches": ["main"],
-      "addLabels": ["target: minor"]
-    },
-    {
-      "matchBaseBranches": ["!main"],
-      "addLabels": ["target: patch"]
-    },
     {
       "enabled": false,
       "matchFileNames": ["tests/legacy-cli/e2e/ng-snapshot/package.json"],