Update os_config_os_policy_assignment.html.markdown

[melinath]

fixed yaml frontmatter formatting

https://developer.hashicorp.com/terraform/registry/providers/docs#yaml-frontmatter

still rendering incorrectly - I think this should fix the issue. It looks correct in the doc preview tool

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
TF Conversion: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))