doc(contributing): Add warning for test --all

[zrosenbauer]

Description:

BREAKING CHANGE:

Related issue (if exists):

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3de6dc3

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[codspeed-hq]

CodSpeed Performance Report

Merging #9338 will improve performances by 5.93%

_{Comparing zrosenbauer:docs/contrib-tests-tip (3de6dc3) with main (acb3952)}

Summary

⚡ 4 improvements
✅ 174 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	zrosenbauer:docs/contrib-tests-tip	Change
⚡	es/visitor/base-perf/boxing_boxed	3.2 µs	3.1 µs	+3.8%
⚡	es/visitor/base-perf/boxing_boxed_clone	2.4 µs	2.3 µs	+3.87%
⚡	es/visitor/base-perf/boxing_unboxed	3.4 µs	3.3 µs	+4.48%
⚡	es/visitor/base-perf/boxing_unboxed_clone	2.6 µs	2.5 µs	+5.93%