doc: fixed some code comment typo.

Signed-off-by: hongliang <513918845@qq.com>
Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: hongliang5316

src/ngx_http_lua_rewriteby.c

@@ -110,7 +110,7 @@ ngx_http_lua_rewrite_handler(ngx_http_request_t *r)
             if (r->header_sent) {
                 dd("header already sent");
 
-                /* response header was already generated in access_by_lua*,
+                /* response header was already generated in rewrite_by_lua*,
                  * so it is no longer safe to proceed to later phases
                  * which may generate responses again */