tests: update nginx to 1.25.3.

Author: zhuizhuhaomeng

.travis.yml

@@ -1,6 +1,10 @@
 sudo: required
 dist: focal
 
+branches:
+  only:
+    - "master"
+
 os: linux
 
 language: c
@@ -36,7 +40,7 @@ env:
     - TEST_NGINX_SLEEP=0.006
   matrix:
     - NGINX_VERSION=1.21.4
-    - NGINX_VERSION=1.25.1
+    - NGINX_VERSION=1.25.3
 
 install:
   - if [ ! -d download-cache ]; then mkdir download-cache; fi