Bump src/deps/pybind11 from a2e59f0 to e6984c8

Bumps [src/deps/pybind11](https://github.com/pybind/pybind11) from `a2e59f0` to `e6984c8`.
- [Release notes](https://github.com/pybind/pybind11/releases)
- [Commits](pybind/pybind11@a2e59f0...e6984c8)

---
updated-dependencies:
- dependency-name: src/deps/pybind11
  dependency-version: e6984c805ec09c0e5f826e3081a32f322a6bfe63
  dependency-type: direct:production
...

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

Author: dependabot[bot]