Bump swedbank-pay-design-guide-jekyll-theme in /tests/full

Bumps [swedbank-pay-design-guide-jekyll-theme](https://github.com/SwedbankPay/swedbank-pay-design-guide-jekyll-theme) from 2.1.7 to 2.1.8.
- [Release notes](https://github.com/SwedbankPay/swedbank-pay-design-guide-jekyll-theme/releases)
- [Commits](SwedbankPay/swedbank-pay-design-guide-jekyll-theme@2.1.7...2.1.8)

---
updated-dependencies:
- dependency-name: swedbank-pay-design-guide-jekyll-theme
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

tests/full/Gemfile.lock

@@ -133,7 +133,7 @@ GEM
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
-    swedbank-pay-design-guide-jekyll-theme (2.1.7)
+    swedbank-pay-design-guide-jekyll-theme (2.1.8)
       faraday (>= 1.0.1, < 3)
       jekyll (>= 3.7, < 5.0)
       jekyll-contentblocks (~> 1, >= 1.2)