Add a tip to limit concurrent tasks

[rumyantseva]

Description

A tiny doc improvement on how to limit concurrent tasks.

Readiness checklist

• I added tests for new functionality or bugfixes.
• I ran task all, and it passed.
• I added/updated comments for both exported and unexported top-level declarations (functions, types, etc).
• I checked comments rendering with task godocs.
• (for maintainers only) I set Reviewers, Assignee, Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[AlekSi]

[codecov]

Codecov Report

Merging #883 (6cb68cd) into main (0d32d56) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #883      +/-   ##
==========================================
- Coverage   59.08%   59.01%   -0.07%     
==========================================
  Files         219      219              
  Lines       10023    10023              
==========================================
- Hits         5922     5915       -7     
- Misses       3403     3411       +8     
+ Partials      698      697       -1     

Impacted Files	Coverage Δ
internal/util/version/version.go	55.00% <0.00%> (-5.00%)	⬇️
internal/handlers/pg/pgdb/pool.go	63.05% <0.00%> (-1.21%)	⬇️
internal/clientconn/conninfo/conn_info.go	83.33% <0.00%> (+16.66%)	⬆️

Flag	Coverage Δ
integration	61.28% <ø> (-0.04%)	⬇️
mongodb	18.52% <ø> (-0.04%)	⬇️
pg	61.21% <ø> (-0.04%)	⬇️
unit	24.72% <ø> (-0.08%)	⬇️

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