Update plugin version to align with sprint

[aaemnnosttv]

Feature Description

The last release of Site Kit was 1.50.0 but the next release will be 1.68.0. This is a one time change to align the plugin version with our sprints as a minor enhancement for project management.

Going forward, our regular sprintly releases will follow the same convention as before, incrementing the minor version for every release, with occasional intermediate releases incrementing the patch portion of the version number.

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Acceptance criteria

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Implementation Brief

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QA Brief

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Changelog entry

• Update plugin version to align with the current sprint.