ci: update dependency ubuntu to v26

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ubuntu	github-runner	major	24.04 → 26.04

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• ✅ Entered queue — 2026-10-02 18:30 UTC · Rule: renovate · triggered by rule Automatic merge on approval
• ✅ Checks passed · in-place
• ✅ Merged — 2026-10-02 18:33 UTC · at 9772a5cc43a5669d271bbe3fbcd72781582a61d4

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