[R] Avoid warnings and prints during tests #13750

Job	Run time
Build CI containers (xgb-ci.gpu_build_rockylinux8)	1m 52s
Build CI containers (xgb-ci.gpu_build_rockylinux8_dev_ver)	1m 59s
Build CI containers (xgb-ci.gpu_build_r_rockylinux8)	2m 5s
Build CI containers (xgb-ci.gpu)	2m 18s
Build CI containers (xgb-ci.cpu)	13m 25s
Build CI containers (xgb-ci.manylinux_2_28_x86_64)	31s
Build CI containers (xgb-ci.manylinux2014_x86_64)	32s
Build CI containers (xgb-ci.manylinux2014_aarch64)	36s
Build CI containers (xgb-ci.aarch64)	1m 7s
Build CPU ARM64 + manylinux_2_28_aarch64 wheel	6m 27s
Build CUDA + manylinux_2_28_x86_64 wheel	10m 9s
Build CUDA with RMM	10m 13s
Build CPU	13m 31s
Build CUDA with RMM (dev)	10m 38s
Build GPU-enabled R package	13m 31s
Build manylinux2014_aarch64 wheel	2m 55s
Build manylinux2014_x86_64 wheel	3m 41s
Run Python tests (single-gpu)	7m 3s
Run Python tests (multiple-gpu)	15m 17s
Run Python tests (cpu-amd64)	9m 25s
Run Python tests (cpu-arm64)	1m 21s
Run Google Tests with GPUs (Suite gpu, Runner linux-amd64-gpu)	4m 30s
Run Google Tests with GPUs (Suite gpu-rmm, Runner linux-amd64-gpu)	4m 33s
Run Google Tests with GPUs (Suite mgpu, Runner linux-amd64-mgpu)	2m 34s
	2h 20m 13s

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