Update dns_pdns.sh

Missing application/json header is causing this PATCH to fail, because it gets processed as form data.

dnsapi/dns_pdns.sh

@@ -207,6 +207,9 @@ _pdns_rest() {
   export _H1="X-API-Key: $PDNS_Token"
 
   if [ ! "$method" = "GET" ]; then
+    if [ "$method" == "PATCH" ]; then
+        export _H2="Content-Type: application/json"
+    fi
     _debug data "$data"
     response="$(_post "$data" "$PDNS_Url$ep" "" "$method")"
   else