chore: delete astro-5 example (#5995)

Remove the `astro-5` example app.

- Deleted `examples/astro-5/` directory
- Removed `astro-5` from the CI examples matrix in
`reusable-examples.yml`

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: qw-in <19194187+qw-in@users.noreply.github.com>

Author: Copilot

.github/workflows/reusable-examples.yml

@@ -115,7 +115,6 @@ jobs:
       matrix:
         folder:
           - astro
-          - astro-5
           - express-bots
           - express-newman
           - express-rate-limit