fix: update SendCloudEventsForRuns default and mark deprecated

[anithapriyanatarajan]

Changes

This PR fixes test failure due to tektoncd/pipeline v1.12.0

(tektoncd/pipeline#9774) deprecated the
send-cloudevents-for-runs feature flag and changed its default from false to true. CloudEvents for CustomRuns are now enabled by default when a sink is configured in config-events.

• Add deprecation comments to PipelineProperties field and SetDefaults
• Fix test expectation: false -> true to match new upstream default

Ref: tektoncd/pipeline#9774

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Release Notes

`send-cloudevents-for-runs` default changed from `false` to `true` to align with
tektoncd/pipeline v1.12.0 (upstream deprecation). The `SendCloudEventsForRuns` field
in `TektonPipeline` spec is now deprecated and will be removed in a future release
IssueRef: https://github.com/tektoncd/operator/issues/3439

[anithapriyanatarajan]

/kind bug

[anithapriyanatarajan]

@vdemeester @jkhelil - This PR fixes the ci failures of #3418

[jkhelil]

thank you @anithapriyanatarajan , can you please

• add a tracking issue for removal and add it to the comment
• Add release note, eventually documentation

[tekton-robot]

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[anithapriyanatarajan]

thank you @anithapriyanatarajan , can you please

• add a tracking issue for removal and add it to the comment
• Add release note, eventually documentation

@jkhelil Issue for tracking - #3430
Added a release note to this PR.

[jkhelil]

/lgtm