Remove use of unsupported pgconn library

[Sovietaced]

Tracking issue

This tracks an open vulnerability in the security tab. CVE-2026-32286

Why are the changes needed?

Removes use of no longer supported library and resolves vulnerability.

What changes were proposed in this pull request?

Remove use of no longer supported library (it is now archived). Bump to latest version of newer library.

This version is used with pgx v4. In pgx v5 it is part of the https://github.com/jackc/pgx repository. This v4 version will reach end-of-life on July 1, 2025. Only security bug fixes will be made to this version.

This is important to improve the readability of release notes.

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

Docs link

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 56.95%. Comparing base (bc223e3) to head (d802b3f).

Files with missing lines	Patch %	Lines
datacatalog/pkg/repositories/errors/postgres.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7217      +/-   ##
==========================================
- Coverage   56.95%   56.95%   -0.01%     
==========================================
  Files         931      931              
  Lines       58234    58229       -5     
==========================================
- Hits        33169    33164       -5     
- Misses      22014    22015       +1     
+ Partials     3051     3050       -1     

Flag	Coverage Δ
unittests-datacatalog	53.51% <0.00%> (ø)
unittests-flyteadmin	53.13% <100.00%> (-0.01%)	⬇️
unittests-flytecopilot	43.06% <ø> (ø)
unittests-flytectl	64.09% <ø> (-0.05%)	⬇️
unittests-flyteidl	75.71% <ø> (ø)
unittests-flyteplugins	60.17% <ø> (ø)
unittests-flytepropeller	53.71% <ø> (ø)
unittests-flytestdlib	62.62% <ø> (+0.04%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.