The argument bias_initializer was not used in _SeparableConv. (#10687)
The argument bias_initializer was not used in _SeparableConv. (#10687)

### Summary

I think it was meant to be passed it to the `__init__` of the parent class.

### Related Issues

### PR Overview

- [ ] This PR requires new unit tests [y/n] (make sure tests are included)
- [ ] This PR requires to update the documentation [y/n] (make sure the docs are up-to-date)
- [ ] This PR is backwards compatible [y/n]
- [x] This PR changes the current API [y/n] (all API changes need to be approved by fchollet)

keras-team/keras,keras-team/keras