chore(deps): 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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[codspeed]

Merging this PR will not alter performance

✅ 10 untouched benchmarks
⏩ 17 skipped benchmarks¹

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_{Comparing renovate/ubuntu-26.x (dde2493) with main (42bf46e)}

Footnotes

1. 17 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU grep testsuite comparison:

Test results comparison:
  Current:   TOTAL: 128 / PASSED: 65 / FAILED: 28 / SKIPPED: 35
  Reference: TOTAL: 128 / PASSED: 78 / FAILED: 29 / SKIPPED: 21

Changes from main branch:
  TOTAL: +0
  PASSED: -13
  FAILED: -1

Test improvements (1):
  + in-eq-out-infloop

[oech3]

@lhecker I agree with this change since this is not used by Ubuntu yet and we want to run GnuTests with newer glibc.
But this bumped min supported glibc ver of https://github.com/uutils/grep/releases/tag/latest-commit .

[lhecker]

@oech3 How big of an issue is that for the uutils project? Personally, I only use rolling distros, and I figured distros that aren't typically prefer building their own packages.

[oech3]

People on legacy distri downloaded pre-built from here might fail to run grep.