📝Fix Docker image tag and Node version mismatch in README.md

[takuya-o]

The Docker image tag in README.md was not correctly set to the version of Node being used. This commit fixes the mismatch by updating the Docker image tag to the correct version.

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Document fix

Proposed changes

Checklist

• [x] I have read the contribution guidelines
• [ ] For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
• [ ] I have run grunt to verify the unit tests pass
• [ ] I have added suitable unit tests to cover the new/changed functionality

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: takuya-o / name: Takuya Ono (d3fe0b7ac18ba2befd1cac141913b27113ca5bf9)