Don't instantiate config client inside oav params

[jacob720]

Instructions to reviewer on how to test:

1. Do thing x
2. Confirm thing y happens

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 99.08%. Comparing base (fe5c9c0) to head (8d903da).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2004      +/-   ##
==========================================
- Coverage   99.08%   99.08%   -0.01%     
==========================================
  Files         319      319              
  Lines       12408    12406       -2     
==========================================
- Hits        12295    12293       -2     
  Misses        113      113              

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