fix https://github.com/acmesh-official/acme.sh/issues/4680

zerossl returns retry-after header within "200 OK" code.
so we don't check the "503" code anymore.

acme.sh

@@ -2222,15 +2222,14 @@ _send_signed_request() {
 
     _CACHED_NONCE="$(echo "$responseHeaders" | grep -i "Replay-Nonce:" | _head_n 1 | tr -d "\r\n " | cut -d ':' -f 2 | cut -d , -f 1)"
 
-    if ! _startswith "$code" "2"; then
     _body="$response"
     if [ "$needbase64" ]; then
     _body="$(echo "$_body" | _dbase64 multiline)"
     _debug3 _body "$_body"
     fi
-
     _retryafter=$(echo "$responseHeaders" | grep -i "^Retry-After *: *[0-9]\+ *" | cut -d : -f 2 | tr -d ' ' | tr -d '\r')
-      if [ "$code" = '503' ]; then
+
+    if [ "$code" = '503' ] || [ "$_retryafter" ]; then
       _sleep_overload_retry_sec=$_retryafter
       if [ -z "$_sleep_overload_retry_sec" ]; then
         _sleep_overload_retry_sec=5
@@ -2241,6 +2240,7 @@ _send_signed_request() {
         continue
       else
         _info "The retryafter=$_retryafter is too large > 600, not retry anymore."
+        return 1
       fi
     fi
     if _contains "$_body" "JWS has invalid anti-replay nonce" || _contains "$_body" "JWS has an invalid anti-replay nonce"; then
@@ -2255,7 +2255,7 @@ _send_signed_request() {
       _sleep $_sleep_retry_sec
       continue
     fi
-    fi
+
     return 0
   done
   _info "Giving up sending to CA server after $MAX_REQUEST_RETRY_TIMES retries."