Bump deps/libtommath from c6a00c2 to 3746c58

Bumps [deps/libtommath](https://github.com/libtom/libtommath) from `c6a00c2` to `3746c58`.
- [Release notes](https://github.com/libtom/libtommath/releases)
- [Commits](libtom/libtommath@c6a00c2...3746c58)

---
updated-dependencies:
- dependency-name: deps/libtommath
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>