docs: Update Canonical Openstack release dates

Hello team,

Canonical Openstack release date table still reports Openstack 2025.1 as "Expected on April 2025".
From what I see on Opendev sunbeam-charms repo, sunbeam it was updated to 2025.1 about 7 months ago: https://opendev.org/openstack/sunbeam-charms/commit/b2f8389a54e0dc4f9d7e1faa9e6203d251b915dc

Also Openstack 2025.2 is reported as "Expected on October 2025", maybe it needs to be updated as well since we're now in November.

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*Reported from: https://canonical-openstack.readthedocs-hosted.com/en/latest/reference/release-cycle-and-supported-versions/*

Start at the reported ReadTheDocs release-cycle-and-supported-versions page and compare the OpenStack 2025.1 and 2025.2 entries with the linked sunbeam-charms commit and the dates stated in the issue. Done means the table no longer shows outdated expected release dates for those versions.

Written by the indexing model from the issue text.