util: Update tinyformat

Updates `tinyformat.h` to commit
c42f/tinyformat@3a33bbf upstream.

Makes sure that our local changes are kept:

- #3767 1b8fd35 Make tinyformat errors raise an exception instead of assert()ing
- #4735 9b6d4c5 Move strprintf define to tinyformat.h
- #4748 6e5fd00 include stdexcept (for std::exception)
- #8000 9eaa0af force USE_VARIADIC_TEMPLATES
- Add `std::string format(const std::string &fmt...` added this
  at the time, as we want to be able to do `strprintf(_(...), ...)`

Inspired by #8264.

Author: laanwj