Bump wkhtmltopdf-binary from 0.12.6.6 to 0.12.6.7

Bumps [wkhtmltopdf-binary](https://github.com/zakird/wkhtmltopdf_binary_gem) from 0.12.6.6 to 0.12.6.7.
- [Release notes](https://github.com/zakird/wkhtmltopdf_binary_gem/releases)
- [Changelog](https://github.com/zakird/wkhtmltopdf_binary_gem/blob/master/CHANGELOG.md)
- [Commits](zakird/wkhtmltopdf_binary_gem@0.12.6.6...0.12.6.7)

---
updated-dependencies:
- dependency-name: wkhtmltopdf-binary
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -555,7 +555,7 @@ GEM
     websocket-extensions (0.1.5)
     wicked_pdf (2.7.0)
       activesupport
-    wkhtmltopdf-binary (0.12.6.6)
+    wkhtmltopdf-binary (0.12.6.7)
     xpath (3.2.0)
       nokogiri (~> 1.8)
     yard (0.9.34)