Bump src/deps/pybind11 from 8a099e4 to 3878c23

Bumps [src/deps/pybind11](https://github.com/pybind/pybind11) from `8a099e4` to `3878c23`.
- [Release notes](https://github.com/pybind/pybind11/releases)
- [Commits](pybind/pybind11@8a099e4...3878c23)

---
updated-dependencies:
- dependency-name: src/deps/pybind11
  dependency-version: 3878c23f8d04a96b647255081a321ae9e32ee7c6
  dependency-type: direct:production
...

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

Author: dependabot[bot]