TRAIN_EVAL.md中的eval Bevformer指令有误

[niouoklul]

./tools/uniad_dist_train.sh ./projects/configs/bevformer/bevformer_base.py UniAD/ckpts/bevformer_r101_dcn_24ep.pth N_GPUS
应该改为
./tools/uniad_dist_eval.sh ./projects/configs/bevformer/base_bevformer.py ./ckpts/bevformer_r101_dcn_24ep.pth N_GPUS