ansible-test - Fix remote completion validation.

changelogs/fragments/ansible-test-remote-completion-validation.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - ansible-test - Fix internal validation of remote completion configuration.

test/lib/ansible_test/_internal/completion.py

@@ -160,6 +160,8 @@ class PosixRemoteCompletionConfig(RemoteCompletionConfig, PythonCompletionConfig
     placeholder: bool = False
 
     def __post_init__(self):
+        super().__post_init__()
+
         if not self.supported_pythons:
             if self.version and not self.placeholder:
                 raise Exception(f'POSIX remote completion entry "{self.name}" must provide a "python" setting.')