ci: schedule ng-snapshot Renovate updates for early morning only

Add a packageRule in `renovate.json` matching `tests/e2e/ng-snapshot/package.json` with `"schedule": ["before 8am"]` so that snapshot dependency update pull requests only open in the morning outside of office hours.

Author: alan-agius4

renovate.json

@@ -4,6 +4,10 @@
   "extends": ["github>angular/dev-infra//renovate-presets/default.json5"],
   "ignorePaths": ["tests/e2e/assets/**", "tests/schematics/update/packages/**"],
   "packageRules": [
+    {
+      "matchFileNames": ["tests/e2e/ng-snapshot/package.json"],
+      "schedule": ["before 8am"]
+    },
     {
       "enabled": false,
       "matchFileNames": ["tests/e2e/ng-snapshot/package.json"],