[CI/CD] Add single version flag during bootstrap to fix version conflicts

[RyanL1997]

Description

On behalf of the change in dashboards core: https://github.com/opensearch-project/OpenSearch-Dashboards/pull/5675. We need to add --single-version=loose flag during the bootstrap step in our CI to manipulate the behavior of single-version validation.

Issues Resolved

• Resolve the CI failure: https://github.com/opensearch-project/dashboards-observability/actions/runs/7964135017/job/21741091909?pr=1447#step:16:231

Check List

• [ ] New functionality includes testing.
  • [ ] All tests pass, including unit test, integration test and doctest
• [ ] New functionality has been documented.
  • [ ] New functionality has javadoc added
  • [ ] New functionality has user manual doc added
• [x] Commits are signed per the DCO using --signoff

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (25f4094) 94.73% compared to head (9111c67) 94.73%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #341 +/- ## ======================================= Coverage 94.73% 94.73% ======================================= Files 5 5 Lines 152 152 Branches 45 45 ======================================= Hits 144 144 Misses 8 8 ```

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