Fix no-changed-when ansible-lint errors

Reference: https://ansible-lint.readthedocs.io/en/latest/default_rules/#no-changed-when

roles/matrix-postgres/tasks/import_postgres.yml

@@ -101,6 +101,9 @@
         and manually run the above import command directly on the server.
 
 - name: Perform Postgres database import
-  ansible.builtin.command: "{{ matrix_postgres_import_command }}"
+  ansible.builtin.command:
+    cmd: "{{ matrix_postgres_import_command }}"
   async: "{{ postgres_import_wait_time }}"
   poll: 10
+  register: matrix_postgres_import_postgres_command_result
+  changed_when: matrix_postgres_import_postgres_command_result.rc == 0