chore(deps): bump wkhtmltopdf-binary from 0.12.6.6 to 0.12.6.8

Bumps [wkhtmltopdf-binary](https://github.com/zakird/wkhtmltopdf_binary_gem) from 0.12.6.6 to 0.12.6.8.
- [Release notes](https://github.com/zakird/wkhtmltopdf_binary_gem/releases)
- [Changelog](https://github.com/zakird/wkhtmltopdf_binary_gem/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zakird/wkhtmltopdf_binary_gem/commits)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -331,7 +331,7 @@ GEM
     websocket-extensions (0.1.5)
     wicked_pdf (2.8.1)
       activesupport
-    wkhtmltopdf-binary (0.12.6.6)
+    wkhtmltopdf-binary (0.12.6.8)
     xpath (3.2.0)
       nokogiri (~> 1.8)
     zeitwerk (2.6.17)