Bump nokogiri from 1.16.7 to 1.18.8 (ministryofjustice#598)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.16.7 to 1.18.8.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.16.7...v1.18.8)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-version: 1.18.8
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Hettie Street <43522239+HettieS@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -153,7 +153,7 @@ GEM
     marcel (1.0.4)
     method_source (1.1.0)
     mini_mime (1.1.5)
-    mini_portile2 (2.8.7)
+    mini_portile2 (2.8.9)
     minitest (5.25.1)
     msgpack (1.7.2)
     mutex_m (0.3.0)
@@ -168,7 +168,7 @@ GEM
     net-smtp (0.5.1)
       net-protocol
     nio4r (2.7.3)
-    nokogiri (1.16.7)
+    nokogiri (1.18.8)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
     notiffany (0.1.3)