fix(sdk) include finally tasks in placeholder indir

[Udiknedormin]

Which issue is resolved by this Pull Request:
Resolves #1034.

Description of your changes:
Include finally tasks in _handle_tekton_pipeline_variables.

Environment tested:

• Python Version (use python --version): 3.9.0
• Tekton Version (use tkn version): 8bcb27213e1a6a0b75e133f2acb60e9be51827e5
• Kubernetes Version (use kubectl version): 0.36.0
• OS (e.g. from /etc/os-release): irrelevant

Checklist:

• The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[Tomcli]

Thanks @Udiknedormin
I will follow up with the test cases PR in your issue to make sure this code won't break in the future.

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Tomcli, Udiknedormin

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