[API Compatibility] fix the loss docs

[zty-king]

这些loss文档存在格式问题或示例不统一，此次全部统一

[paddle-bot]

感谢你贡献飞桨文档，文档预览构建中，Docs-New 跑完后即可预览，预览链接：http://preview-pr-7611.paddle-docs-preview.paddlepaddle.org.cn/documentation/docs/zh/api/index_cn.html
预览工具的更多说明，请参考：飞桨文档预览工具

[github-actions]

📚 本次 PR 文档预览链接（点击展开）

ℹ️ 预览提醒 请等待 Docs-NEW 流水线运行完成后再点击预览链接，否则可能会看到旧版本内容或遇到链接无法访问的情况。

• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.BCELoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.BCEWithLogitsLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.CosineEmbeddingLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.CrossEntropyLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.HingeEmbeddingLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.KLDivLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.L1Loss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.MSELoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.MarginRankingLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.MultiLabelMarginLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.MultiLabelSoftMarginLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.MultiMarginLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.NLLLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.PoissonNLLLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.SmoothL1Loss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.SoftMarginLoss.md: 点击预览
• docs/guides/model_convert/convert_from_pytorch/api_difference/torch_more_args/torch.nn.TripletMarginLoss.md: 点击预览