fix: openresty bats global-flag test uses settable key

The previous regression case selected `--openresty-global-hsts`, but `hsts` is rejected by `openresty:set --global` because it is not in the plugin's GLOBAL_KEYS list. Switch to `--openresty-letsencrypt-server`, which the bats setup already pins to a known staging URL, so the test exercises the same `--global --<info-flag>` parsing path without needing a separate set step.

tests/unit/openresty.bats

@@ -18,22 +18,12 @@ teardown() {
   dokku nginx:start
 }
 
-@test "(openresty:report) --global --openresty-global-hsts" {
-  run /bin/bash -c "dokku openresty:set --global hsts false"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-
-  run /bin/bash -c "dokku openresty:report --global --openresty-global-hsts"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-  assert_output "false"
-
-  run /bin/bash -c "dokku openresty:set --global hsts"
+@test "(openresty:report) --global --openresty-letsencrypt-server" {
+  run /bin/bash -c "dokku openresty:report --global --openresty-letsencrypt-server"
   echo "output: $output"
   echo "status: $status"
   assert_success
+  assert_output "https://acme-staging-v02.api.letsencrypt.org/directory"
 }
 
 @test "(openresty) openresty:help" {