Suppress warning in test-io

[IndrajeetPatil]

Closes #1161

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (10efce2) 92.16% compared to head (4447865) 92.16%.

:exclamation: Current head 4447865 differs from pull request most recent head aac55d7. Consider uploading reports for the commit aac55d7 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1169 +/- ## ======================================= Coverage 92.16% 92.16% ======================================= Files 46 46 Lines 2655 2655 ======================================= Hits 2447 2447 Misses 208 208 ```

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[IndrajeetPatil]

@lorenzwalthert Can we deal with this flaky test? It is making it more likely that we miss out an actual failing test.

══ Failed tests ════════════════════════════════════════════════════════════════
── Failure ('tests-cache-require-serial.R:28:3'): top-level test: Caches top-level expressions efficiently on style_text() ──
full_cached_benchmark["elapsed"] * 30 is not strictly less than benchmark["elapsed"]. Difference: 0.01

[lorenzwalthert]

Yeah let's lift the hurdle for failing, e.g. x20 instead of x 30?

[lorenzwalthert]

Sounds good, thanks for implementing. If you want, you can also add the fix for the offending unrelated test to this PR.