fix(dbmanager): use correct SQL to drop databases

Previously the code used:

```
DROP DATABASE mydb IF EXISTS WITH (FORCE)
```

which is not standard SQL and does not work with PostgreSQL.

This patch fixes to code to issue:

```
DROP DATABASE IF EXISTS mydb WITH (FORCE)
```

internal/dbmanager/client.go

@@ -106,7 +106,7 @@ func (m *ManagedClient) CreateDatabase(ctx context.Context, req *CreateDatabaseR
 
  conn, err := pgx.Connect(ctx, uri.String())
  if err != nil {
- pool.Exec(ctx, fmt.Sprintf(`DROP DATABASE "%s" IF EXISTS WITH (FORCE)`, name))
+ pool.Exec(ctx, fmt.Sprintf(`DROP DATABASE IF EXISTS "%s" WITH (FORCE)`, name))
  return nil, fmt.Errorf("connect %s: %s", name, err)
  }
  defer conn.Close(ctx)
@@ -123,7 +123,7 @@ func (m *ManagedClient) CreateDatabase(ctx context.Context, req *CreateDatabaseR
  }
 
  if migrationErr != nil {
- pool.Exec(ctx, fmt.Sprintf(`DROP DATABASE "%s" IF EXISTS WITH (FORCE)`, name))
+ pool.Exec(ctx, fmt.Sprintf(`DROP DATABASE IF EXISTS "%s" WITH (FORCE)`, name))
  return nil, migrationErr
  }