docs: fix explicit env vars docs version

[WarningImHack3r]

#15934 was created before Kit 2.62 got released, thus its docs updates naturally indicated 2.62 as a target version. However, 2.62 got released before merging this PR (or not including it). As a result, the "since version" is erroneous.

This PR fixes this by bumping the numbers everywhere the original PR set them to 2.63, which actually includes the change.

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Latest commit: 3995c50

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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