[CI] Remove testing on 6, 8, 15, 16 threads (#396) #2452

Job	Run time
clang-format	15s
python-lint	7s
ubuntu-gcc-build (ubuntu-24.04)	1m 15s
ubuntu-gcc-build (ubuntu-24.04-arm)	1m 37s
windows-msvc-build	3m 48s
ubuntu-clang-build (ubuntu-24.04)	1m 14s
ubuntu-clang-build (ubuntu-24.04-arm)	2m 41s
windows-clang-build	4m 33s
macos-clang-build	1m 56s
ubuntu-gcc-test (ubuntu-24.04-arm)	6m 9s
ubuntu-gcc-test (ubuntu-24.04)	5m 27s
macos-clang-test	2m 57s
ubuntu-clang-test (ubuntu-24.04)	4m 29s
ubuntu-clang-test (ubuntu-24.04-arm)	6m 9s
ubuntu-clang-sanitizer-build (ubuntu-24.04)	1m 14s
windows-msvc-test	2m 23s
ubuntu-clang-sanitizer-test (ubuntu-24.04)	3m 11s
windows-clang-test	1m 16s
macos-clang-test-extended	2m 10s
windows-clang-test-extended	1m 29s
windows-msvc-test-extended	1m 26s
ubuntu-clang-sanitizer-test-extended (ubuntu-24.04)	1m 26s
ubuntu-gcc-test-extended (ubuntu-24.04-arm)	3m 56s
ubuntu-gcc-test-extended (ubuntu-24.04)	2m 32s
ubuntu-clang-test-extended (ubuntu-24.04)	2m 40s
ubuntu-clang-test-extended (ubuntu-24.04-arm)	3m 20s
ubuntu-gcc-build-codecov	3m 16s
ubuntu-gcc-build-perf-stats	-1s
	1h 12m 55s

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