[CI] Remove testing on 6, 8, 15, 16 threads #2450

Job	Run time
clang-format	9s
python-lint	6s
ubuntu-gcc-build (ubuntu-24.04-arm)	2m 31s
ubuntu-gcc-build (ubuntu-24.04)	59s
ubuntu-clang-build (ubuntu-24.04)	1m 50s
ubuntu-clang-build (ubuntu-24.04-arm)	2m 12s
windows-clang-build	3m 30s
windows-msvc-build	2m 14s
macos-clang-build	1m 47s
macos-clang-test	3m 9s
ubuntu-clang-sanitizer-build (ubuntu-24.04)	1m 15s
ubuntu-clang-test (ubuntu-24.04-arm)	6m 4s
ubuntu-clang-test (ubuntu-24.04)	4m 32s
windows-msvc-test	2m 22s
ubuntu-gcc-test (ubuntu-24.04-arm)	5m 10s
ubuntu-gcc-test (ubuntu-24.04)	4m 13s
ubuntu-clang-sanitizer-test (ubuntu-24.04)	1m 56s
windows-clang-test	1m 23s
windows-msvc-test-extended	1m 20s
macos-clang-test-extended	2m 11s
windows-clang-test-extended	1m 19s
ubuntu-clang-sanitizer-test-extended (ubuntu-24.04)	56s
ubuntu-gcc-test-extended (ubuntu-24.04-arm)	3m 51s
ubuntu-gcc-test-extended (ubuntu-24.04)	2m 33s
ubuntu-clang-test-extended (ubuntu-24.04)	2m 41s
ubuntu-clang-test-extended (ubuntu-24.04-arm)	3m 39s
ubuntu-gcc-build-codecov	4m 5s
ubuntu-gcc-build-perf-stats	-1s
	1h 7m 56s

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