Update tags formatting in writing guide

[Fashander]

Description

Closes #2847

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), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Merging #3097 (23df6b2) into main (110cfa0) will decrease coverage by 0.09%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3097      +/-   ##
==========================================
- Coverage   76.61%   76.53%   -0.09%     
==========================================
  Files         388      388              
  Lines       21287    21287              
==========================================
- Hits        16310    16292      -18     
- Misses       4052     4066      +14     
- Partials      925      929       +4     

see 7 files with indirect coverage changes

Flag	Coverage Δ
hana	?
integration	73.11% <ø> (-0.10%)	⬇️
mongodb	5.46% <ø> (ø)
pg	66.43% <ø> (-0.04%)	⬇️
shard-1	56.96% <ø> (-0.07%)	⬇️
shard-2	55.12% <ø> (-0.04%)	⬇️
shard-3	57.19% <ø> (ø)
sqlite	46.47% <ø> (-0.07%)	⬇️
unit	24.02% <ø> (ø)

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