Use literal block scalar for changelog replace string

[adamtheturtle]

Use literal block scalar (|) with actual newlines instead of escape sequences in the release workflow. This fixes zizmor warnings while being compatible with yamlfix.

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Note

Updates the release workflow to use a YAML literal block (|) with real newlines for the replace value in the "Update changelog" step.

• Changes .github/workflows/release.yml to replace the inline escaped string with a block scalar for inserting the release heading in CHANGELOG.rst.

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