fix: bump default postgres version to 15.6

[sweatybridge]

What kind of change does this PR introduce?

feature

What is the new behavior?

Upgrade postgres locally to 15.6 by default.

Additional context

Add any other context or screenshots.

[coveralls]

Pull Request Test Coverage Report for Build 11810522544

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 842 unchanged lines in 48 files lost coverage.
• Overall coverage decreased (-0.2%) to 59.649%

---

Files with Coverage Reduction	New Missed Lines	%
internal/utils/slice.go	1	86.96%
internal/logout/logout.go	1	94.12%
internal/projects/apiKeys/api_keys.go	1	95.65%
internal/db/test/test.go	1	81.25%
cmd/stop.go	1	71.43%
cmd/status.go	2	37.5%
cmd/seed.go	2	50.0%
internal/hostnames/common.go	2	9.2%
internal/utils/console.go	2	95.24%
internal/unlink/unlink.go	2	87.5%

Totals
Change from base Build 10097759648:	-0.2%
Covered Lines:	6386
Relevant Lines:	10706

---

💛 - Coveralls