chore: update @oclif/core to latest version

[shazron]

This is to support adobe/aio-cli#781

Summary

Update @oclif/core from 1.26.2 to the latest version (4.9.0).

Current state

@adobe/aio-cli-plugin-app-templates@2.0.3 depends on @oclif/core@1.26.2.

Desired state

Update to @oclif/core@4.9.0 (latest).

Notes

• Review the oclif/core changelog for breaking changes between v1 and v4.
• This is part of a broader effort to update all aio-cli plugins to the latest @oclif/core.

[aiojbot]

JIRA issue created: https://jira.corp.adobe.com/browse/ACNA-4421

[shazron]

PR #73