refactor(backend): remove dataset.merge_protocols

[eatyourgreens]

Now that protocols are created per group, not per subject, there's no need to dedupe subject protocols.

[sonarcloud[bot]]

Quality Gate passed for 'pkpdapp'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarcloud[bot]]

Quality Gate passed for 'pkpdapp-team_pkpdapp_frontend'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.24%. Comparing base (99d55c0) to head (ddd8442).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #494 +/- ## =============================================== - Coverage 76.50% 76.24% -0.26% =============================================== Files 108 108 Lines 5609 5591 -18 =============================================== - Hits 4291 4263 -28 - Misses 1318 1328 +10 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.