[TorchComms] Update readme on cp and async tp

[mori360]

Remove them from known issues
cp
TEST_BACKEND=nccl TRAIN_FILE=torchtitan.experiments.torchcomms.train CONFIG_FILE="./torchtitan/models/llama3/train_configs/debug_model.toml" ./run_train.sh --parallelism.context_parallel_degree 2

[rank0]:[titan] 2025-10-21 11:50:24,918 - root - INFO - step: 1 loss: 8.2808 grad_norm: 1.4344 memory: 0.60GiB(0.63%) tps: 884 tflops: 0.06 mfu: 0.01%
[rank0]:[titan] 2025-10-21 11:50:24,918 - root - INFO - Synchronizing and adjusting timeout for all ProcessGroups to 0:01:40
[rank0]:[titan] 2025-10-21 11:50:25,010 - root - INFO - step: 2 loss: 7.9722 grad_norm: 1.5075 memory: 0.65GiB(0.68%) tps: 89,241 tflops: 6.39 mfu: 0.65%
[rank0]:[titan] 2025-10-21 11:50:25,133 - root - INFO - step: 3 loss: 7.2171 grad_norm: 1.9729 memory: 0.67GiB(0.70%) tps: 66,834 tflops: 4.78 mfu: 0.48%
[rank0]:[titan] 2025-10-21 11:50:25,261 - root - INFO - step: 4 loss: 6.3402 grad_norm: 2.3603 memory: 0.67GiB(0.70%) tps: 64,239 tflops: 4.60 mfu: 0.46%
[rank0]:[titan] 2025-10-21 11:50:25,355 - root - INFO - step: 5 loss: 5.3055 grad_norm: 2.6067 memory: 0.67GiB(0.70%) tps: 87,354 tflops: 6.25 mfu: 0.63%
[rank0]:[titan] 2025-10-21 11:50:25,447 - root - INFO - step: 6 loss: 4.7225 grad_norm: 2.6398 memory: 0.67GiB(0.70%) tps: 89,556 tflops: 6.41 mfu: 0.65%
[rank0]:[titan] 2025-10-21 11:50:25,888 - root - INFO - step: 7 loss: 4.3229 grad_norm: 2.1676 memory: 0.67GiB(0.70%) tps: 18,607 tflops: 1.33 mfu: 0.13%
[rank0]:[titan] 2025-10-21 11:50:25,971 - root - INFO - step: 8 loss: 4.0035 grad_norm: 1.6869 memory: 0.67GiB(0.70%) tps: 98,424 tflops: 7.05 mfu: 0.71%
[rank0]:[titan] 2025-10-21 11:50:26,059 - root - INFO - step: 9 loss: 3.9520 grad_norm: 1.3777 memory: 0.67GiB(0.70%) tps: 93,815 tflops: 6.72 mfu: 0.68%
[rank0]:[titan] 2025-10-21 11:50:26,173 - root - INFO - step: 10 loss: 3.6494 grad_norm: 1.3774 memory: 0.67GiB(0.70%) tps: 72,228 tflops: 5.17 mfu: 0.52%
[rank0]:[titan] 2025-10-21 11:50:26,336 - root - INFO - Dumping profiler traces at step 10
[rank0]:[titan] 2025-10-21 11:50:26,372 - root - INFO - Finished dumping profiler traces in 0.04 seconds
[rank0]:[titan] 2025-10-21 11:50:26,373 - root - INFO - Dumping memory snapshot at step 10

async tp