update test2

Author: AlinsRan

t/upstream_mtls2.t

@@ -32,7 +32,7 @@ run_tests;
 
 __DATA__
 
-=== TEST 1: send client certificate
+=== TEST 1: only set client certificate
 --- config
     location /t {
         access_by_lua_block {
@@ -62,13 +62,13 @@ __DATA__
         proxy_ssl_name admin.apisix.dev;
         proxy_pass https://unix:$TEST_NGINX_HTML_DIR/nginx.sock:/foo;
     }
-
---- response_body
-ok
+--- error_code: 502
+--- error_log
+unable to verify the first certificate
 
 
 
-=== TEST 2: send ca certificate
+=== TEST 2: send valid client certificate
 --- config
     location /t {
         access_by_lua_block {