fix: add missing error check for WriteChangelogState in initiateApplier

[ajm188]

The WriteChangelogState call at line 1365 was missing error handling, which could cause the migration to fail silently if the changelog table was not properly created. This manifested as a "Table doesn't exist" error later in the migration process.

All other calls to WriteChangelogState in the codebase properly check for errors, so I'm guessing this was just overlooked

A Pull Request should be associated with an Issue.

Relates to #1622. This doesn't actually solve "why didn't the changelog table get created in my migration" but it does handle the error when trying to write to that table.

We wish to have discussions in Issues. A single issue may be targeted by multiple PRs.
If you're offering a new feature or fixing anything, we'd like to know beforehand in Issues,
and potentially we'll be able to point development in a particular direction.

Related issue: https://github.com/github/gh-ost/issues/0123456789

Further notes in https://github.com/github/gh-ost/blob/master/.github/CONTRIBUTING.md
Thank you! We are open to PRs, but please understand if for technical reasons we are unable to accept each and any PR

Description

This PR [briefly explain what it does]

In case this PR introduced Go code changes:

• contributed code is using same conventions as original code
• script/cibuild returns with no formatting errors, build errors or unit test errors.

[meiji163]

Thanks for catching that!