Handle 42P07 PostgreSQL error to fix the tests

[rumyantseva]

Description

This PR is created to fix failing tests on main, e.g. here.

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.

[codecov]

Codecov Report

Merging #895 (34bb02d) into main (6071465) will decrease coverage by 2.09%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #895      +/-   ##
==========================================
- Coverage   61.24%   59.15%   -2.10%     
==========================================
  Files         182      225      +43     
  Lines        8605    10020    +1415     
==========================================
+ Hits         5270     5927     +657     
- Misses       2690     3399     +709     
- Partials      645      694      +49     

Impacted Files	Coverage Δ
internal/handlers/pg/pgdb/collections.go	53.04% <0.00%> (+5.21%)	⬆️
internal/util/version/version.go	55.00% <0.00%> (-5.00%)	⬇️
internal/handlers/tigris/msg_dbstats.go	0.00% <0.00%> (ø)
...nal/handlers/tigris/msg_getfreemonitoringstatus.go	0.00% <0.00%> (ø)
internal/handlers/tigris/msg_findandmodify.go	0.00% <0.00%> (ø)
internal/handlers/tigris/msg_ismaster.go	0.00% <0.00%> (ø)
internal/handlers/tigris/msg_datasize.go	0.00% <0.00%> (ø)
internal/tjson/tjson.go	51.77% <0.00%> (ø)
internal/handlers/tigris/msg_dropdatabase.go	0.00% <0.00%> (ø)
internal/tjson/int32.go	45.45% <0.00%> (ø)
... and 89 more

Flag	Coverage Δ
integration	61.49% <0.00%> (+0.25%)	⬆️
mongodb	18.44% <0.00%> (-0.06%)	⬇️
pg	61.42% <0.00%> (+0.25%)	⬆️
unit	24.59% <0.00%> (?)

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