Update release.yaml to avoid command substitution on Markdown

[shouth]

Description

• Update .github/workflows/Release.yaml to avoid shell command substituion on Markdown content

Abstract

Existing workflow directly expands Markdown content to shell command. If expanded Markdown contains code spans like this, workflow applys command substitution on them. This PR update workflow to store Markdown content before generating release_description.txt to avoid command substitution.

Background

When PR description is written like this:

PR description is expanded into command in GitHub Actions,

and command substitution is conducted.

Details

Assign ${{ github.event.pull_request.body }} to the environment variable $PULL_REQUEST_BODY and output it to release_description.txt.

References

https://github.com/tier4/scenario_simulator_v2/actions/runs/7985003102/job/21802726254

Destructive Changes

N/A

Known Limitations

N/A

[github-actions]

Checklist for reviewers ☑️

All references to "You" in the following text refer to the code reviewer.

• Is this pull request written in a way that is easy to read from a third-party perspective?
• Is there sufficient information (background, purpose, specification, algorithm description, list of disruptive changes, and migration guide) in the description of this pull request?
• If this pull request contains a destructive change, does this pull request contain the migration guide?
• Labels of this pull request are valid?
• All unit tests/integration tests are included in this pull request? If you think adding test cases is unnecessary, please describe why and cross out this line.
• The documentation for this pull request is enough? If you think adding documents for this pull request is unnecessary, please describe why and cross out this line.