pipebackend-abi-version has been removed in 4.0.0.
We no longer need this setting explained in the master doc.
outgoing AXFR. Note that if your slaves do not support ALIAS, they will return
NODATA for A/AAAA queries for such names.
-## `pipebackend-abi-version`
-* Integer
-* Default: 1
-* Removed in: 4.0.0 (is now specific to the backend)
-
-ABI version to use for the pipe backend. See
-["PipeBackend protocol"](backend-pipe.md#pipebackend-protocol).
-
## `prevent-self-notification`
* Boolean
* Default: yes