Skip tests for enable setFreeMonitoring for MongoDB

[chilagrow]

Description

Closes #{issue_number}.

Free monitoring cannot be enabled anymore https://www.mongodb.com/docs/manual/reference/command/setFreeMonitoring/

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Merging #3318 (2d58431) into main (302ef22) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3318      +/-   ##
==========================================
- Coverage   75.26%   75.22%   -0.04%     
==========================================
  Files         400      400              
  Lines       23559    23559              
==========================================
- Hits        17731    17722       -9     
- Misses       4797     4805       +8     
- Partials     1031     1032       +1     

Flag	Coverage Δ
hana	?
integration	71.83% <ø> (-0.06%)	⬇️
mongodb	5.01% <ø> (-0.02%)	⬇️
pg	62.11% <ø> (-0.01%)	⬇️
shard-1	56.09% <ø> (ø)
shard-2	54.79% <ø> (-0.04%)	⬇️
shard-3	54.89% <ø> (ø)
sqlite	55.60% <ø> (-0.06%)	⬇️
unit	24.59% <ø> (ø)

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[rumyantseva]