670 remove mockito

[Relm-Arrowny]

Fixes #670
Removed mockito dependence.
During which I have to altered test_converter_eq() in test_converter_eq.py to match/improve coverage.

Instructions to reviewer on how to test:

1. Run unit test
2. Confirm all test passes.

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 94.51%. Comparing base (9bfa98f) to head (dc4e513).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #711      +/-   ##
==========================================
+ Coverage   94.49%   94.51%   +0.02%     
==========================================
  Files         110      110              
  Lines        4376     4376              
==========================================
+ Hits         4135     4136       +1     
+ Misses        241      240       -1     

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[DominicOram]

Great, thank you!