Update I19-2 backlight

[noemifrisina]

Update the backlight device for I19-2 after epics PV change (and move to cluster)

BL19I-EA-IOC-12:AD1:choiceButton -> BL19I-EA-BL-02:choiceButton

Instructions to reviewer on how to test:

1. Run dodal connect and verify backlight is there

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 99.28%. Comparing base (c44a61c) to head (8f5d34c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2206   +/-   ##
=======================================
  Coverage   99.28%   99.28%           
=======================================
  Files         366      366           
  Lines       14367    14367           
=======================================
  Hits        14264    14264           
  Misses        103      103           

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