fix typo

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 76e949c..de2b970 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1951,7 +1951,7 @@
 
         if (size == 0) {
             ngx_log_error(NGX_LOG_ALERT, c->log, 0,
-                          "upstream buffer is too small to read repsonse");
+                          "upstream buffer is too small to read response");
             ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
             return;
         }