@Jitendra Rai
Thanks for clarification. I came to the same problem.
However the following is working in my environment:
<LocalizedString ElementType="ClaimType" ElementId="signInName" StringId="DisplayName">Please enter your email</LocalizedString>
Be sure to empty your browser cache. I had some trouble with old settings due to browser caching.
There seems to be another issue as well.
In the doc we read:
Added a UXString heading in addition to intro to display on the page as a title. This is hidden by default.
However, this heading is never rendered in html. It's even not hidden.