tests: bumped the NGINX core to 1.29.4.

Author: zhuizhuhaomeng

.travis.yml

@@ -41,7 +41,7 @@ env:
     - NGX_BUILD_JOBS=$JOBS
     - TEST_NGINX_SLEEP=0.006
   matrix:
-    - NGINX_VERSION=1.29.2 OPENSSL_VER=3.5.4 OPENSSL_PATCH_VER=3.5.4
+    - NGINX_VERSION=1.29.4 OPENSSL_VER=3.5.4 OPENSSL_PATCH_VER=3.5.4
 
 services:
  - memcache