Update doc string for apple2_undulator.set as it breaks CI

error when running `tox -e tests `locally
```
===================================================================== FAILURES ======================================================================
______________________________________________ [doctest] src.dodal.devices.apple2_undulator.Apple2.set ______________________________________________
483 and polarisation.
484 This method should be implemented by the beamline specific ID class as the
485 motor positions will be different for each beamline depending on the
486 undulator design and the lookup table used.
487 _set can be used to set the motor positions for the given energy and
488 polarisation provided that all motors can be moved at the same time.
489
490 Examples
491 --------
492 >>> RE( id.set(888.0)) # This will set the ID to 888 eV
UNEXPECTED EXCEPTION: NameError("name 'RE' is not defined")
Traceback (most recent call last):
File "/usr/local/lib/python3.11/doctest.py", line 1355, in __run
exec(compile(example.source, filename, "single",
File "", line 1, in
NameError: name 'RE' is not defined
/workspaces/dodal/src/dodal/devices/apple2_undulator.py:492: UnexpectedException
--------------------------------------------------------------- Captured stdout setup ---------------------------------------------------------------
adding handler (INFO)> to logger , at level: 20
adding handler to logger , at level: 10
Logging to INFO file handler tmp/dev/dodal.log
adding handler to logger , at level: 20
Logging to DEBUG handler tmp/dev/debug/dodal.log
adding handler to logger , at level: 10
...
============================================================== short test summary info ==============================================================
FAILED src/dodal/devices/apple2_undulator.py::src.dodal.devices.apple2_undulator.Apple2.set
==================================================== 1 failed, 1306 passed, 2 skipped in 42.19s =====================================================
ERROR: InvocationError for command /venv/bin/pytest -m 'not requires' (exited with code 1)
______________________________________________________________________ summary _______________
```