Update dependency ubuntu to v26

[olehermanse]

This PR contains the following updates:

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

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.73%. Comparing base (6c193d1) to head (9bf641f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #241   +/-   ##
=======================================
  Coverage   54.73%   54.73%           
=======================================
  Files          33       33           
  Lines        4149     4149           
=======================================
  Hits         2271     2271           
  Misses       1878     1878           

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[SimonThalvorsen]

Any reason to not just use ubuntu-latest?

[olehermanse]

In general we prefer to pin dependencies, and update them with PRs.