Fix #2804 make submission baseline documentation update

[snehasuresh2005]

This PR updates the documentation in the make_submission_public_private_baseline.md file to include a section on how the challenge host can make a submission as the baseline submission.

1. Added new section explaining the process for making a submission as the baseline.
2. Clarified steps and responsibilities for the challenge host.
   Testing Steps:
   Since this is a documentation update, no testing is required for functionality. Please verify the accuracy and clarity of the new instructions provided.
   Hi team,
   Thank you for reviewing this PR! Please let me know if anything needs further clarification or modification.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.30%. Comparing base (96968d6) to head (385608e).
Report is 1113 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4436      +/-   ##
==========================================
- Coverage   72.93%   69.30%   -3.63%     
==========================================
  Files          83       20      -63     
  Lines        5368     3574    -1794     
==========================================
- Hits         3915     2477    -1438     
+ Misses       1453     1097     -356     

see 64 files with indirect coverage changes

see 64 files with indirect coverage changes

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