travis-ci: bumped the NGINX core to 1.19.9. (#235)

Author: xiaocang

.travis.yml

@@ -37,9 +37,9 @@ env:
     - TEST_NGINX_SLEEP=0.006
   matrix:
     - NGINX_VERSION=1.17.8 OPENSSL_VER=1.0.2u
-    - NGINX_VERSION=1.19.3 OPENSSL_VER=1.0.2u
-    - NGINX_VERSION=1.19.3 OPENSSL_VER=1.1.0l
-    - NGINX_VERSION=1.19.3 OPENSSL_VER=1.1.1f
+    - NGINX_VERSION=1.19.9 OPENSSL_VER=1.0.2u
+    - NGINX_VERSION=1.19.9 OPENSSL_VER=1.1.0l
+    - NGINX_VERSION=1.19.9 OPENSSL_VER=1.1.1f
 
 services:
  - memcache