Fix update-examples-cron workflow failing on forks with Vault auth errors

[Copilot]

The update-examples-cron workflow runs every 8 hours and attempts to authenticate with Grafana's internal Vault infrastructure. On forked repositories, this fails with 401 Unauthorized, causing repeated workflow failures.

Changes

• Added repository check to update-examples-cron job to skip execution on non-Grafana repositories
• Aligns with existing pattern used in update-contributors.yml and update-make-docs.yml

jobs:
  update-examples-cron:
    if: github.repository == 'grafana/pyroscope'
    runs-on: ${{ github.repository_owner == 'grafana' && 'ubuntu-x64-small' || 'ubuntu-latest' }}

The workflow will now skip gracefully on forks instead of failing authentication.

Original prompt

Reference: https://github.com/FuzzysTodd/pyroscope/commit/caa23019755452df902366b28dfa6fd431831f3b/checks?check_suite_id=54339096553fix

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