remove baseUrl config in tsconfig.json

[ruanyl]

Description

This "baseUrl": ".", is not needed, it prevent us to use path alias such import {} from "opensearch-dashboards/public" and import {} from "opensearch-dashboards/server"

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test.
• New functionality has user manual doc added.
• Commits are signed per the DCO using --signoff.

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