ci: bumped the OpenSSL to 1.1.1p. (#297)

Author: Johnny Wang

.travis.yml

@@ -40,7 +40,7 @@ env:
     - TEST_NGINX_SLEEP=0.006
   matrix:
     - NGINX_VERSION=1.21.4 OPENSSL_VER=1.1.0l
-    - NGINX_VERSION=1.21.4 OPENSSL_VER=1.1.1n
+    - NGINX_VERSION=1.21.4 OPENSSL_VER=1.1.1p
 
 services:
  - memcache