Revert "add RepPoints support (#1256)" (#1263)

configs/reppoints/README.md

configs/reppoints/bbox_r50_grid_center_fpn_1x.py

configs/reppoints/bbox_r50_grid_fpn_1x.py

configs/reppoints/reppoints.png

configs/reppoints/reppoints_minmax_r50_fpn_1x.py

configs/reppoints/reppoints_moment_r101_dcn_fpn_2x.py

configs/reppoints/reppoints_moment_r101_dcn_fpn_2x_mt.py

configs/reppoints/reppoints_moment_r101_fpn_2x.py

configs/reppoints/reppoints_moment_r101_fpn_2x_mt.py

configs/reppoints/reppoints_moment_r50_fpn_1x.py

configs/reppoints/reppoints_moment_r50_fpn_2x.py

configs/reppoints/reppoints_moment_r50_fpn_2x_mt.py

configs/reppoints/reppoints_moment_x101_dcn_fpn_2x.py

configs/reppoints/reppoints_moment_x101_dcn_fpn_2x_mt.py

configs/reppoints/reppoints_partial_minmax_r50_fpn_1x.py

mmdet/core/anchor/__init__.py

mmdet/core/anchor/point_generator.py

mmdet/core/anchor/point_target.py

mmdet/core/bbox/assigners/__init__.py

mmdet/core/bbox/assigners/point_assigner.py