composer(deps-dev): bump rector/rector from 1.2.5 to 1.2.6

Bumps [rector/rector](https://github.com/rectorphp/rector) from 1.2.5 to 1.2.6.
- [Release notes](https://github.com/rectorphp/rector/releases)
- [Commits](rectorphp/rector@1.2.5...1.2.6)

---
updated-dependencies:
- dependency-name: rector/rector
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>