[BUG] Breaking changes workflow should not run on main

[dblock]

Describe the bug

Breaking changes are expected on main. Currently the job introduced in #12974 is failing on push.

Related component

Build

To Reproduce

https://github.com/opensearch-project/OpenSearch/actions/runs/8525228788/job/23351663380

Expected behavior

Main build to be green.

Additional Details

No response

[peternied]

@dblock Thanks for creating this issue, rather than have this test fail on build should it do some other action for just pull request vs push? Even if intentional, change that break the public API will break the builds of downstream plugins.

While in main we certainly make breaking changes, often changes are make specifically to go into the next release in the downstream 2.x branches.

[dblock]

What's the baseline for the failure, meaning will it ever be green for PRs on main?