chore: remove references to dbtestutil.WillUsePostgres (#20436)

Addresses https://github.com/coder/internal/issues/758.

This PR only cleans up dead code, it makes no changes to test logic.

coderd/autobuild/lifecycle_executor_test.go

@@ -776,10 +776,6 @@ func TestExecutorWorkspaceAutostopNoWaitChangedMyMind(t *testing.T) {
 }
 
 func TestExecutorAutostartMultipleOK(t *testing.T) {
-	if !dbtestutil.WillUsePostgres() {
-		t.Skip(`This test only really works when using a "real" database, similar to a HA setup`)
-	}
-
 	t.Parallel()
 
 	var (
@@ -1259,10 +1255,6 @@ func TestNotifications(t *testing.T) {
 func TestExecutorPrebuilds(t *testing.T) {
 	t.Parallel()
 
-	if !dbtestutil.WillUsePostgres() {
-		t.Skip("this test requires postgres")
-	}
-
 	// Prebuild workspaces should not be autostopped when the deadline is reached.
 	// After being claimed, the workspace should stop at the deadline.
 	t.Run("OnlyStopsAfterClaimed", func(t *testing.T) {