Increase timeout for tests

[rumyantseva]

Description

As tests start failing due to timeout, let's increase it as a quick fix.

Readiness checklist

• I added/updated unit tests.
• I added/updated integration/compatibility tests.
• 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), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Merging #2508 (9e0cb6f) into main (ca200f5) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2508   +/-   ##
=======================================
  Coverage   65.09%   65.09%           
=======================================
  Files         400      400           
  Lines       19776    19776           
=======================================
  Hits        12874    12874           
  Misses       5976     5976           
  Partials      926      926           

see 1 file with indirect coverage changes

Flag	Coverage Δ
integration	58.03% <ø> (ø)
mongodb	5.11% <ø> (ø)
pg	57.96% <ø> (ø)
unit	25.65% <ø> (+0.02%)	⬆️

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