numfmt: fix #11935 --invalid=warn/ignore/fail ignores mode when rejecting scientific notation

[Devel08]

This PR resolves #11935.

When I fixed the issue where scientific notation is accepted, but it shouldn't be, I manually returned an error instead of letting "result" to do that. I fixed that and I apologize.
Ran cargo fmt and cargo test.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/pipe-f (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)

[codspeed-hq]

Merging this PR will not alter performance

✅ 309 untouched benchmarks
⏩ 46 skipped benchmarks¹

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_{Comparing Devel08:fix-#11935 (690faf7) with main (22bd036)}

Footnotes

1. 46 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. ↩

[cakebaker]

Can you please add a test to tests/by_util/test_numfmt.rs to ensure we don't regress in the future? Thanks.

[Devel08]

@cakebaker Sure

[codspeed-hq]

Unable to generate the performance report

There was an internal error while processing the run's data. We're working on fixing the issue. Feel free to contact us on Discord or at support@codspeed.io if the issue persists.

[cakebaker]

Thanks!