Fix and apply update source script

[gassmoeller]

The current source update script renames prescribed_traction_boundary_indicators into prescribed_boundary_traction_indicators, which is inconsistent with our writing of prescribed_velocity_boundary_indicators. Fix that by excluding those cases from the replacement. Not sure why I did not notice this earlier.
Also there is one occurrence of tracers that was not properly replaced, because it was an open pull request at the time I applied the script to the repository.

[tjhei]

Looks good. Have you tried applying the scripts to the .ccs in tests/ benchmarks/ and cookbooks/ to make sure it doesn't change anything?

[gassmoeller]

Yes, I applied the script to all .cc and .h files in the main repo and the one particle change was the only generated diff.

[tjhei]

👍