chore(deps): Update ubuntu:26.04 Docker digest

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ubuntu (source)	final	digest	6fee4ab → 889d056
ubuntu (source)	stage	digest	6fee4ab → 889d056

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[lusoris]

Superseded by #1130, which batches this update together with 35 other pending dependency PRs into a single branch and a single CI run.

Batching was necessary: 45 concurrent dependency PRs could not drain through the merge gate (see #1127 / ADR-1123), and the full macOS/ARM/CUDA/SYCL matrix is disproportionate for a one-line manifest edit. Your change is included verbatim in #1130 — where a minor and a major targeted the same dependency, the major won.

Renovate will reopen this if #1130 does not land.