rgw_rest_user_policy: [55603] Fix Get & List User Policy responses

rgw_rest_user_policy: [55603] Fix Get & List User Policy responses

GetUserPolicy & ListUserPolicies responses has few mistakes/typos if compared
with aws documentation of the API's.
While using `aws iam` cli the mistakes in the response schema causes the
blank/incorrect response output.
Correcting the same with the patch.

Fixes: https://tracker.ceph.com/issues/55603
Signed-off-by: Sumedh A. Kulkarni <sumedh.a.kulkarni@seagate.com>
(cherry picked from commit 4b8c66a074f3491129e1864388f980b812f47752)

Conflicts:
	src/rgw/rgw_rest_user_policy.cc

Cherry-pick notes:
- Conflict due to try/catch block in RGWListUserPolicies::execute not present in Quincy