Update to work with next version of ophyd-async

[DominicOram]

Update to work with bluesky/ophyd-async#646. Wait for that to be merged + new ophyd-async release before merging this.

Instructions to reviewer on how to test:

1. Confirm tests still pass

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.63%. Comparing base (f896461) to head (c518f75).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #899      +/-   ##
==========================================
- Coverage   95.63%   95.63%   -0.01%     
==========================================
  Files         128      128              
  Lines        5271     5268       -3     
==========================================
- Hits         5041     5038       -3     
  Misses        230      230              

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