On a Flow board, go to a topic's action menu and choose Lock topic.

Result: the textarea that appears inside the topic titlebar has no placeholder text. There's no placeholder attribute in the flow_topic_titlebar_lock.handlebars template.

Expected: the placeholder text should guide the user as to what to say, and hint as to what happens to the text. It's already confusing with the Summarize text.

i18n has "flow-moderation-placeholder-lock-topic": "Please {{GENDER:$3|explain}} why you're locking this topic." Better is "Please {{GENDER:$3|give}} the reason why you're locking this topic"