Bump library/ubuntu from 24.04 to 26.04

Bumps library/ubuntu from 24.04 to 26.04.

---
updated-dependencies:
- dependency-name: library/ubuntu
  dependency-version: '26.04'
  dependency-type: direct:production
...

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Author: dependabot[bot]

Dockerfile.updater-core

@@ -1,5 +1,5 @@
 # syntax=docker.io/docker/dockerfile:1.20
-FROM docker.io/library/ubuntu:24.04
+FROM docker.io/library/ubuntu:26.04
 
 ARG TARGETARCH