Latest TUF repos aren't compatible with R11

[jgallagher]

Attempting to upgrade london from R11 to a TUF repo from an omicron branch (#7171, but the particular changes there are not relevant to this issue), wicketd rejected the TUF repo:

Error: error uploading repository to wicketd

Caused by:
    Error Response: status: 400 Bad Request; headers: {"content-type": "application/json", "x-request-id": "27164afb-4aa6-4442-95ce-802fa16509c5", "content-length": "128", "date": "Wed, 27 Nov 2024 17:21:14 GMT"}; value: Error { error_code: None, message: "duplicate board found for kind `GimletSp`: `gimlet-b`", request_id: "27164afb-4aa6-4442-95ce-802fa16509c5" }

The TUF repos we're currently emitting include both production and lab SP images:

$ unzip -l tuf-mupdate.zip | grep gimlet_sp
  4960915  01-01-1980 00:00   repo/targets/e74417c557c0602c2ef20ef25b4e7ae17a07dc643a96d115f45eabf26c98e9df.gimlet_sp-gimlet-e-lab-1.0.32.tar.gz
  4871611  01-01-1980 00:00   repo/targets/556dcf6416e6da79d49657c0cf77d02e286ba28dc481f92e87136c44b1e9f329.gimlet_sp-gimlet-f-1.0.32.tar.gz
  4960968  01-01-1980 00:00   repo/targets/80a404f5f083d1852234b20ed1c0fbb5d72ebf16f9e470a5b8460314a8cff31b.gimlet_sp-gimlet-f-lab-1.0.32.tar.gz
  4961191  01-01-1980 00:00   repo/targets/ffb7ff447a32ba773c22a494bc1e59bb779ea70086a33947fe56476d32b11f42.gimlet_sp-gimlet-c-lab-1.0.32.tar.gz
  4869252  01-01-1980 00:00   repo/targets/d761c7f19bb33c9250c847ce83ade57a137013b8497ffa81e4ded85014571dd0.gimlet_sp-gimlet-c-1.0.32.tar.gz
  4961126  01-01-1980 00:00   repo/targets/becf55bfe3938abf945cc1fdda84dc317520a5baf6799b13e445c304cfebf4a0.gimlet_sp-gimlet-d-lab-1.0.32.tar.gz
  4871584  01-01-1980 00:00   repo/targets/7f6cf23a3cf26fe9c7a40a76d7e2be8a418723ef505786c8e41df89fd8d1f77e.gimlet_sp-gimlet-d-1.0.32.tar.gz
  4869206  01-01-1980 00:00   repo/targets/f2fcb24dbb85a8be78235226fc95dd183250f75819bc813befdf5a166a72acd0.gimlet_sp-gimlet-b-1.0.32.tar.gz
  4871509  01-01-1980 00:00   repo/targets/c9cb6c6d2b3fd9e198074b4160119caa21ca88632b218420a570725ffd0b8616.gimlet_sp-gimlet-e-1.0.32.tar.gz
  4961397  01-01-1980 00:00   repo/targets/38bef602690696cf41b44c5bf32a3306d8c52dcd66b7dc33b2a03369f741d7cd.gimlet_sp-gimlet-b-lab-1.0.32.tar.gz

#6867 taught wicketd how to deal with these, but that change isn't in R11. A fix for this would be to remove the lab images from our TUF repos until after R12 is out the door; I'm not sure if there are any alternatives to that.