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/database/dbtestutil/db.go

@@ -23,13 +23,6 @@ import (
 	"github.com/coder/coder/v2/testutil"
 )
 
-// WillUsePostgres returns true if a call to NewDB() will return a real, postgres-backed Store and Pubsub.
-// TODO(hugodutka): since we removed the in-memory database, this is always true,
-// and we need to remove this function. https://github.com/coder/internal/issues/758
-func WillUsePostgres() bool {
-	return true
-}
-
 type options struct {
 	fixedTimezone string
 	dumpOnFailure bool
@@ -75,10 +68,6 @@ func withReturnSQLDB(f func(*sql.DB)) Option {
 func NewDBWithSQLDB(t testing.TB, opts ...Option) (database.Store, pubsub.Pubsub, *sql.DB) {
 	t.Helper()
 
-	if !WillUsePostgres() {
-		t.Fatal("cannot use NewDBWithSQLDB without PostgreSQL, consider adding `if !dbtestutil.WillUsePostgres() { t.Skip() }` to this test")
-	}
-
 	var sqlDB *sql.DB
 	opts = append(opts, withReturnSQLDB(func(db *sql.DB) {
 		sqlDB = db