Add small tweaks

[AlekSi]

Description

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Add labels.

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 #3377 (3b6c8ee) into main (8425016) will decrease coverage by 1.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3377      +/-   ##
==========================================
- Coverage   74.08%   73.04%   -1.04%     
==========================================
  Files         414      414              
  Lines       25330    25330              
==========================================
- Hits        18766    18503     -263     
- Misses       5464     5695     +231     
- Partials     1100     1132      +32     

Files Changed	Coverage
internal/handlers/pg/msg_createindexes.go	100.00%
internal/handlers/sqlite/msg_createindexes.go	100.00%

Flag	Coverage Δ
integration	69.85% <100.00%> (-1.19%)	⬇️
mongodb-1	4.72% <0.00%> (ø)
pg-1	43.75% <33.33%> (+0.03%)	⬆️
pg-2	43.48% <33.33%> (ø)
pg-3	44.03% <0.00%> (+0.11%)	⬆️
sqlite-1	42.71% <33.33%> (+0.10%)	⬆️
sqlite-2	42.11% <33.33%> (ø)
sqlite-3	?
unit	23.31% <0.00%> (ø)

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[rumyantseva]