[t] Fix failed tests in apicast-policy-3scale-batcher.t

Previously context.apply() is set in PR#1038. Due to ctx_ref
is nil in the test, the context also has nil value. However in
openresty 1.21.4 set ngx.ctx to a non-table value is considered
harmful and will return error. Therefore, we need to remove
context.apply() from the test.

Ref: openresty/lua-resty-core#333

t/apicast-policy-3scale-batcher.t

@@ -401,7 +401,6 @@ auth cache on every request (see rewrite_by_lua_block).
 --- upstream env
   location /api-backend {
     rewrite_by_lua_block {
-      require('resty.ctx').apply()
       ngx.shared.cached_auths:flush_all()
     }
      echo 'yay, api backend';
@@ -583,7 +582,6 @@ auth cache on every request (see rewrite_by_lua_block).
 --- upstream env
   location /api-backend {
     rewrite_by_lua_block {
-      require('resty.ctx').apply()
       ngx.shared.cached_auths:flush_all()
     }
      echo 'yay, api backend';