travis-ci: upgraded openssl to 1.1.1l.

Author: xiaocang

.travis.yml

@@ -41,7 +41,7 @@ env:
     - LUACHECK_VER=0.21.1
   matrix:
     - NGINX_VERSION=1.19.9 OPENSSL_VER=1.1.0l OPENSSL_PATCH_VER=1.1.0d
-    - NGINX_VERSION=1.19.9 OPENSSL_VER=1.1.1k OPENSSL_PATCH_VER=1.1.1f
+    - NGINX_VERSION=1.19.9 OPENSSL_VER=1.1.1l OPENSSL_PATCH_VER=1.1.1f
 
 services:
   - memcache