Add CLA note to CONTRIBUTING.md #1543

Job	Run time
unittests-extended / linux-job	17m 14s
onnx / linux-job	4m 48s
unittests-linux (3.10, linux.12xlarge, cpu) / linux-job	22m 40s
unittests-linux (3.11, linux.12xlarge, cpu) / linux-job	21m 19s
unittests-linux (3.8, linux.12xlarge, cpu) / linux-job	22m 56s
unittests-macos (3.10, macos-12) / macos-job	2m 25s
unittests-linux (3.8, linux.g5.4xlarge.nvidia.gpu, cuda, 11.8) / linux-job	56s
unittests-linux (3.9, linux.12xlarge, cpu) / linux-job	22m 54s
unittests-macos (3.11, macos-12) / macos-job	2m 47s
unittests-macos (3.8, macos-12) / macos-job	2m 29s
unittests-macos (3.8, macos-m1-12) / macos-job	1m 17s
unittests-macos (3.9, macos-12) / macos-job	2m 48s
unittests-windows (3.10, windows.4xlarge, cpu) / windows-job	3m 17s
unittests-windows (3.11, windows.4xlarge, cpu) / windows-job	2m 56s
unittests-windows (3.8, windows.4xlarge, cpu) / windows-job	3m 20s
unittests-windows (3.8, windows.g5.4xlarge.nvidia.gpu, cuda, 11.8) / windows-job	3m 11s
unittests-windows (3.9, windows.4xlarge, cpu) / windows-job	3m 46s
	2h 21m 3s

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