fix directive name in error message: "realip_from" to "set_realip_from"

src/http/modules/ngx_http_realip_module.c

diff --git a/src/http/modules/ngx_http_realip_module.c b/src/http/modules/ngx_http_realip_module.c
index c962b51..e134702 100644
--- a/src/http/modules/ngx_http_realip_module.c
+++ b/src/http/modules/ngx_http_realip_module.c
@@ -347,7 +347,7 @@
 
     if (cidr.family != AF_INET) {
         ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
-                           "\"realip_from\" supports IPv4 only");
+                           "\"set_realip_from\" supports IPv4 only");
         return NGX_CONF_ERROR;
     }