gp: Send list of keys instead of dict to remove

gp: Send list of keys instead of dict to remove

`cache_get_all_attribute_values` returns a dict whereas we need to pass
a list of keys to `remove`. These will be interpolated in the gpdb search.

Signed-off-by: Gabriel Nagy <gabriel.nagy@canonical.com>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: David Mulder <dmulder@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Mon Aug 28 03:01:22 UTC 2023 on atb-devel-224

(cherry picked from commit 7dc181757c76b881ceaf1915ebb0bfbcf5aca83a)