Add ssm:TerminateSession action to OIDC role policy

[andrewmooreio]

A follow-up to the previous PR to add various permissions to allow SSH over SSM for our GitHub Workflows:
#5384

The session can be established, however it cannot close cleanly without the ssm:TerminateSession action permission. Adding it back in.

[github-actions]

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Setting default tflint config...
Running tflint --init...
Installing `terraform` plugin...
Installed `terraform` (source: github.com/terraform-linters/tflint-ruleset-terraform, version: 0.2.1)
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[markgov]

LGTM