fix typo

files/cert2json.py

@@ -35,7 +35,7 @@ JSON_FILE = "/etc/acme/{}.json".format(PROVIDER)
 
 
 with open(YAML_FILE, "w") as yaml_out:
-    yaml_out.write("---\n".format(PROVIDER_STRING))
+    yaml_out.write("---\n")
     for txt_line in DECODED_OUTPUT:
         if "Certificate Name:" in txt_line:
             txt_line_out = re.sub('.*Certificate Name: ', '  ', txt_line) + ":"