If Bill doesn't think `/docs/api` is worth linking to, get rid of it

[mccalluc]

In hubmapconsortium/portal-ui#2060, I had proposed linking to /docs/apis from /apis, to provide more detail. Bill does not think it's worth linking to, and proposed this edit:

- [All API microservices](/docs/apis) developed by the IEC are documented at
- [SmartAPI](https://smart-api.info/registry?q=hubmap).
+ The  [HuBMAP Entity API](https://smart-api.info/ui/0065e419668f3336a40d1f5ab89c6ba3)
+ can be used to create, update and retrieve provenance entities which consist of 
+ three base types donors, tissue samples and datasets.

• If we don't think documentation is worth linking to, you should get rid of it.
• You should find any remaining references and fix them.
• You should replace apis.md with apis.redirect.