chore: fix windows postgres tests (#15593)

Patches tests that caused Windows Postgres CI in
https://github.com/coder/coder/pull/15520 to consistently fail.

I tested this by temporarily adding Postgres Windows CI to this PR.
However, I reverted those changes to merge them with
https://github.com/coder/coder/pull/15520. For reference, here's [a
passing CI
run](https://github.com/coder/coder/actions/runs/11918816662/job/33219786238)
from an earlier commit.

**Note:** Although Windows tests now pass, they remain quite flaky. I
recommend running Postgres Windows CI to gather data on these flakes,
but I don’t think it should be a required job just yet.

coderd/workspacestats/activitybump_test.go

@@ -170,7 +170,7 @@ func Test_ActivityBumpWorkspace(t *testing.T) {
 
 				var (
 					now   = dbtime.Now()
-					ctx   = testutil.Context(t, testutil.WaitShort)
+					ctx   = testutil.Context(t, testutil.WaitLong)
 					log   = testutil.Logger(t)
 					db, _ = dbtestutil.NewDB(t, dbtestutil.WithTimezone(tz))
 					org   = dbgen.Organization(t, db, database.Organization{})