Got rid of 2 parameters in Response::build_404()

Instead of passing the `bookName` and `bookTitle` parameters to
`Response::build_404()`, `withTaskbarInfo()` is applied to its result
when needed. Note, that in `InternalServer::handle_raw()`
`withTaskbarInfo()` was not utilized since the results of the `/raw`
endpoint are not supposed to be decorated with a taskbar.
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f