Steps to replicate the issue (include links if applicable):

• Create a basic input box on a project that is not using English
• Set placeholder text
• Hover the input box

What happens?:

• A popup shows "Please fill out this field."

What should have happened instead?:

• This should call a message (such as the messages inputbox-* used for the other interface elements) that can be translated or localized

Software version (skip for WMF-hosted wikis like Wikipedia):

• (WMF Production)

Other information (browser name/version, screenshots, etc.):