Fix "list native roles" task (#779)

This commit fix "List Native Roles" task with Elasticsearch 7.11.0+
by removing the unused `body_format` parameter from `uri` module.

This parameter isn't used with a GET method but make request fail with
`request [GET /_security/role] does not support having a body` error
with Elasticsearch 7.11.0+.

Author: jmlrt

tasks/xpack/security/elasticsearch-security-native.yml

@@ -137,7 +137,6 @@
   uri:
     url: "{{ es_api_uri }}/{{ es_security_api }}/role"
     method: GET
-    body_format: json
     user: "{{es_api_basic_auth_username}}"
     password: "{{es_api_basic_auth_password}}"
     force_basic_auth: yes