delete work_dir in all configs (#2315)

...cos_x101_64x4d_fpn_gn-head_mstrain_640-800_4x2_2x_coco.py

configs/foveabox/fovea_align_r101_fpn_gn-head_4x4_2x_coco.py

...vea_align_r101_fpn_gn-head_mstrain_640-800_4x4_2x_coco.py

configs/foveabox/fovea_align_r50_fpn_gn-head_4x4_2x_coco.py

...ovea_align_r50_fpn_gn-head_mstrain_640-800_4x4_2x_coco.py

configs/foveabox/fovea_r50_fpn_4x4_1x_coco.py

configs/fp16/faster_rcnn_r50_fpn_fp16_1x_coco.py

configs/fp16/mask_rcnn_r50_fpn_fp16_1x_coco.py

configs/fp16/retinanet_r50_fpn_fp16_1x_coco.py

...igs/free_anchor/retinanet_free_anchor_r101_fpn_1x_coco.py

configs/free_anchor/retinanet_free_anchor_r50_fpn_1x_coco.py

...ee_anchor/retinanet_free_anchor_x101-32x4d_fpn_1x_coco.py

configs/gcnet/mask_rcnn_r50_fpn_r16_gcb_c3-c5_1x_coco.py

configs/gcnet/mask_rcnn_r50_fpn_r4_gcb_c3-c5_1x_coco.py

configs/gcnet/mask_rcnn_r50_fpn_syncbn-backbone_1x_coco.py

...ask_rcnn_r50_fpn_syncbn-backbone_r16_gcb_c3-c5_1x_coco.py

...mask_rcnn_r50_fpn_syncbn-backbone_r4_gcb_c3-c5_1x_coco.py

configs/ghm/retinanet_ghm_r50_fpn_1x_coco.py

configs/gn+ws/faster_rcnn_r50_fpn_gn_ws-all_1x_coco.py

configs/gn+ws/mask_rcnn_r50_fpn_gn_ws-all_20_23_24e_coco.py