[CBeds] [Central Bedfordshire] Add special update behaviour

[dracos]

For https://github.com/mysociety/societyworks/issues/5411

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.13%. Comparing base (c973330) to head (e20b43b).
⚠️ Report is 2 commits behind head on cbd-aurora-reviewed.

Files with missing lines	Patch %	Lines
perllib/FixMyStreet/Cobrand/CentralBedfordshire.pm	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##           cbd-aurora-reviewed    #5878   +/-   ##
====================================================
  Coverage                83.13%   83.13%           
====================================================
  Files                      491      491           
  Lines                    36855    36864    +9     
  Branches                  6041     6044    +3     
====================================================
+ Hits                     30638    30647    +9     
+ Misses                    4448     4447    -1     
- Partials                  1769     1770    +1     

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[neprune]

Nice 👍