Clarify MongoDB version

[AlekSi]

Description

We have three options:

• say "MongoDB" or "modern MongoDB" (implying that we are not stuck in pre-5.0 days);
• say "MongoDB 5.0+" or similar (implying the same);
• say "MongoDB 7.0+" or similar (that's the version we actively test).

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 #3653 (166f43f) into main (329efdf) will decrease coverage by 0.65%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3653      +/-   ##
==========================================
- Coverage   62.59%   61.94%   -0.65%     
==========================================
  Files         430      430              
  Lines       27887    27887              
==========================================
- Hits        17455    17274     -181     
- Misses       9411     9574     +163     
- Partials     1021     1039      +18     

see 19 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	58.59% <ø> (-0.61%)	⬇️
hana-1	?
integration	58.59% <ø> (-0.64%)	⬇️
mongodb-1	4.42% <ø> (ø)
postgresql-1	42.91% <ø> (-0.31%)	⬇️
postgresql-2	40.24% <ø> (-0.33%)	⬇️
postgresql-3	42.53% <ø> (-0.36%)	⬇️
sort-false	58.59% <ø> (-0.19%)	⬇️
sort-true	?
sqlite-1	42.32% <ø> (-0.19%)	⬇️
sqlite-2	39.69% <ø> (-0.23%)	⬇️
sqlite-3	41.84% <ø> (-0.55%)	⬇️
unit	22.70% <ø> (-0.05%)	⬇️

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

[Fashander]

Is "latest MongoDB" an option here for "modern MongoDB"? I'm guessing it can be latest MongoDB wire protocol

[AlekSi]

The wire protocol did not change since 5.0

[Fashander]

In that case, "modern MongoDB" is apt, as it covers beyond pre-5.0