Minor follow-up to [[https://github.com/bitcoin/bitcoin/pull/19845 | core#19845]] (D10720).
The template was thought to be needed to handle both `std::ios_base::failure` and `std::runtime_error`, but they both inherit `std:eexception` so it is not necessary.
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/20033 | core#20033]]