Reorganize account data, receipts and presence request regexps in generic_worker docs (#17954)

POST requests for account data, receipts and presence require the worker
to be configured as a stream writer. The regular expressions in the
default list don't assume any HTTP method, so if the worker is not a
stream writer, the request fails.

The stream writer section of the documentation lists the same regexps as
the one I'm removing, so people configuring stream writers can still
configure their routing properly.

More context:
https://github.com/element-hq/synapse/issues/17243#issuecomment-2493621645