acme_challenge_cert_helper: fix bad module.fail_json() call (#51795)

* Fix bad module.fail_json() call.

* Add changelog.

changelogs/fragments/51795-acme_challenge_cert_helper-module-fail.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+- "acme_challenge_cert_helper - the module no longer crashes when the required ``cryptography`` library cannot be found."

lib/ansible/modules/crypto/acme/acme_challenge_cert_helper.py

@@ -179,7 +179,7 @@ def main():
         ),
     )
     if not HAS_CRYPTOGRAPHY:
-        module.fail(msg='cryptography >= 1.3 is required for this module.')
+        module.fail_json(msg='cryptography >= 1.3 is required for this module.')
 
     try:
         # Get parameters