yum_repository: Do not set default value for async (#76750)

* yum_repository: Do not set default value for async

The `async` repository option is deprecated in RHEL 8, but Ansible sets

```ini
async = 1
```

even when it's omitted from the module options, which causes `dnf` to complain
about an unknown configuration option.

This commit removes the default value from the `async` parameter, which means
it won't be added to the repository file if omitted from the module parameters.

Signed-off-by: Benoît Knecht <bknecht@protonmail.ch>

* Document the specific versions with the default True and the option deprecation for RHEL 8

Co-authored-by: s-hertel <19572925+s-hertel@users.noreply.github.com>

changelogs/fragments/75364-yum-repository-async.yml

@@ -0,0 +1,2 @@
+minor_changes:
+- yum_repository - do not give the ``async`` parameter a default value anymore, since this option is deprecated in RHEL 8. This means that ``async = 1`` won't be added to repository files if omitted, but it can still be set explicitly if needed.

lib/ansible/modules/yum_repository.py

@@ -23,8 +23,11 @@ options:
     description:
       - If set to C(yes) Yum will download packages and metadata from this
         repo in parallel, if possible.
+      - In ansible-core 2.11, 2.12, and 2.13 the default value is C(true).
+      - This option has been deprecated in RHEL 8. If you're using one of the
+        versions listed above, you can set this option to None to avoid passing an
+        unknown configuration option.
     type: bool
-    default: 'yes'
   bandwidth:
     description:
       - Maximum available network bandwidth in bytes/second. Used with the
@@ -648,7 +651,7 @@ def main():
         username=dict(),
     )
 
-    argument_spec['async'] = dict(type='bool', default=True)
+    argument_spec['async'] = dict(type='bool')
 
     module = AnsibleModule(
         argument_spec=argument_spec,