Update schedule.json to reduce v25.x Maintenance

[aduh95]

We've discussed in the Release WG meeting about how having long maintenance put a too heavy burden for security releases. For example, we did release Node.js 23.11.1 after Node.js 24.0.0, which takes probably more volunteer time that it brings value to the community.

I suggest we reduce the maintenance window, I picked 2026-05-06 because 24.0.0 was released on 2025-05-06 (so as long as 26.0.0 is not as delayed as 24.0.0 was, we don't have a gap where v25.x is EoL before v26.x is released).

wdyt?

[targos]

Do we have a document that describes our general support policy (with the length of each period)?

[aduh95]

Not really, not for odd-numbered release lines at least. There's https://github.com/nodejs/Release?tab=readme-ov-file#release-plan:

Release/README.md

Lines 105 to 124 in cd5a754

	New *semver-major* releases of Node.js are branched from `main` every six
	months. New even-numbered versions are released in April and odd-numbered
	versions in October.
	In coordination with a new *odd-numbered* major release, the previous
	*even-numbered* major version will transition to Long Term Support. The
	transition to Long Term Support will happen in a *semver-minor* release and
	should happen after the new major version is released.
	Every even (LTS) major version will be actively maintained for 12 months from
	the date it enters LTS coverage. Following those 12 months of active support,
	the major version will transition into "maintenance" mode for 18 months. Prior
	to Node.js 12, the active period was 18 months and the maintenance period 12
	months. See [Releases Phases](#release-phases) for details of which changes
	are expected to land during each release phase.
	The exact date that a release will be moved to LTS, moved between LTS modes,
	or deprecated will be chosen no later than the first day of the month it is to
	change. If the release team plans to change the release date, it will be done
	with no less than 14 days notice.

[targos]

Then I think we should debate and land a change to that document. Then we update the schedule accordingly.