chore(release): 2.6.0 [skip ci]

# [2.6.0](v2.5.0...v2.6.0) (2021-03-11)

### Bug Fixes

* **passenger:** various fixes ([7271c9d](7271c9d))
* **pkg:** add inline EPEL repo configuration for Amazon Linux 2 ([ae6375c](ae6375c))

### Continuous Integration

* **gemfile+lock:** use `ssf` customised `kitchen-docker` repo [skip ci] ([123d13e](123d13e))
* **kitchen+ci:** make rubocop happy [skip ci] ([eedfc56](eedfc56))
* **kitchen+ci:** use latest pre-salted images (after CVE) [skip ci] ([63d32a4](63d32a4))
* **kitchen+gitlab-ci:** use latest pre-salted images [skip ci] ([b4411c6](b4411c6))
* **pre-commit:** update hook for `rubocop` [skip ci] ([2a23743](2a23743))

### Features

* **config:** validate config before applying ([b396b24](b396b24))

### Tests

* **config:** fix for Amazon Linux 2 & Oracle Linux 7/8 ([ab39c8f](ab39c8f))