Remove useless JS operation for relative time tooltips (#20756)

Remove useless JS operation for relative time tooltips (#20756)

This operation that shifts the content from title to data-content is
useless when we can directly render the expected HTML instead.

This change does prevent these tooltips from working when the user has
JS disabled in their browser, but I think we made it clear by now that
JS is required for gitea to work properly.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>