fix grammar

src/core/ngx_connection.c

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 226dc1e..28c904b 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -593,7 +593,7 @@
 
     if (c == NULL) {
         ngx_log_error(NGX_LOG_ALERT, log, 0,
-                      "%ui worker_connections is not enough",
+                      "%ui worker_connections are not enough",
                       ngx_cycle->connection_n);
 
         /* ngx_mutex_unlock */