Fix tests

[AlekSi]

Description

Previous tests might create capped collections in other databases.

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 #3871 (0942d4a) into main (23714a4) will decrease coverage by 6.51%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3871      +/-   ##
==========================================
- Coverage   76.16%   69.65%   -6.51%     
==========================================
  Files         317      317              
  Lines       24027    24027              
==========================================
- Hits        18300    16737    -1563     
- Misses       4663     6159    +1496     
- Partials     1064     1131      +67     

see 72 files with indirect coverage changes

Flag	Coverage Δ
filter-true	65.01% <ø> (-7.45%)	⬇️
hana-1	?
integration	65.01% <ø> (-7.45%)	⬇️
mongodb-1	5.27% <ø> (ø)
postgresql-1	52.23% <ø> (-0.02%)	⬇️
postgresql-2	50.76% <ø> (+0.05%)	⬆️
postgresql-3	?
sqlite-1	51.48% <ø> (ø)
sqlite-2	?
sqlite-3	?
unit	30.45% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[rumyantseva]