DM-33932: Remove the spectraction dataset type

[mfisherlevine]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (8116dd0) 85.63% compared to head (fafc0e0) 85.63%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #793   +/-   ##
=======================================
  Coverage   85.63%   85.63%           
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  Files         266      266           
  Lines       35180    35180           
  Branches     7380     7380           
=======================================
  Hits        30127    30127           
  Misses       3735     3735           
  Partials     1318     1318           

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[timj]

This looks okay given the removal notice that no-one should have ever really used the storage class. Removing a storage class makes it impossible to access a dataset.