Docs have incorrect pointers to schema files

## What are the schemas that are affected by the issue
Probably all, definitely profile (https://github.com/adobe/xdm/blob/master/docs/reference/context/profile.schema.md)
and extensibility base schema
(https://github.com/adobe/xdm/blob/master/docs/reference/common/extensible.schema.md)

The links look like this:
https://github.com/adobe/xdm/blob/master/docs/reference/context/context/profile.schema.json

and should be changed to look like this:
https://github.com/adobe/xdm/blob/master/schemas/context/profile.schema.json

Start with docs/reference/context/profile.schema.md and docs/reference/common/extensible.schema.md, then search the documentation for links containing the duplicated context path. Update affected pointers to the corresponding schemas/... paths and verify that the documented schema links resolve correctly.

Written by the indexing model from the issue text.