Motivation / Background

Fix typo in initialization.md

Detail

finishers → finisher

defines bootstrap, railtie, and finisher initializers, so finishers is mistake

Additional information

none

Checklist

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• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.