Add `pybind11/stl.h` again.

... and make sure it stays.

Change-Id: Iab9f9e9445545a9c97aefd4d83691a70fde2b1c8
Reviewed-on: https://code-review.googlesource.com/c/re2/+/63111
Reviewed-by: Paul Wankadia <junyer@google.com>
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
1 file changed