Bump nokogiri from 1.10.5 to 1.10.9 in /example_app (#19)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.5 to 1.10.9.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.5...v1.10.9)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

example_app/Gemfile.lock

@@ -105,7 +105,7 @@ GEM
     minitest (5.12.2)
     msgpack (1.3.1)
     nio4r (2.5.2)
-    nokogiri (1.10.5)
+    nokogiri (1.10.9)
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
     prometheus-client (0.9.0)