Fix Dependency Review API response error handling

[felickz]

Bug: Failures in the Dependency Review API response are not properly handled due to an oktokit version mismatch

Fixes:

• downgrade octokit/request-error to ^2.1.0
  • supported by actions/core ^1.10.0 (see)
• Add integration test to invoke API (to avoid mocking a response that is dependent on the version of actions/core used) and validate exception response
• Enhanced Forbidden error message back to user to hint that a culprit might also be lack of GitHub Advanced Security for a private repo

Graph Disabled / Private Repo w/o GHAS

Before:

::error::Forbidden

After:

::error::Dependency review is not supported on this repository. Please ensure that Dependency graph is enabled along with GitHub Advanced Security on private repositories, see https://github.com/OWNER/REPO/settings/security_analysis

[felickz]

Integration Test fails with 3.0.2

Succeeds with 2.1.0

[felickz]

Close in favor official PR https://github.com/actions/dependency-review-action/pulls # 370