Created by: huangjun12
Add cn_doc of dropout series: (1) paddle.nn.functional.dropout(x, p=0.5, axis=None, training=True, mode="upscale_in_train”, name=None) (2) paddle.nn.functional.dropout2d(x, p=0.5, training=True, name=None) (3) paddle.nn.functional.dropout3d(x, p=0.5, training=True, name=None) (4) paddle.nn.functional.alpha_dropout(x, p=0.5, training=True, name=None) (5) paddle.nn.Dropout(p=0.5, axis=None, mode="upscale_in_train”, name=None) (6) paddle.nn.Dropout2D(p=0.5, data_format='NCHW', name=None) (7) paddle.nn.Dropout3D(p=0.5, data_format='NCDHW', name=None) (8) paddle.nn.AlphaDropout(p=0.5, name=None)