Fixing MySQL error when inserting fractional datetimes on MySQL versi…

[sobotklp]

Pull Request check-list

Please make sure to review and check all of these items:

• [y] Does npm run test or npm run test-DIALECT pass with this change (including linting)?
• [y] Does your issue contain a link to existing issue (Closes #[issue]) or a description of the issue you are solving?
• [y] Have you added new tests to prevent regressions?
• [n] Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• [n] Have you added an entry under Future in the changelog?

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Description of change

The MySQL dialect no longer emits timezone when writing Fractional dates (sub-second precision)

[janmeier]

Thanks :) - I've updated the changelog accordingly