Bump loofah from 2.2.3 to 2.3.1

Bumps [loofah](https://github.com/flavorjones/loofah) from 2.2.3 to 2.3.1.
- [Release notes](https://github.com/flavorjones/loofah/releases)
- [Changelog](https://github.com/flavorjones/loofah/blob/master/CHANGELOG.md)
- [Commits](flavorjones/loofah@v2.2.3...v2.3.1)

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

Gemfile.lock

@@ -69,7 +69,7 @@ GEM
       simplecov (>= 0.7)
       term-ansicolor
       thor
-    crass (1.0.4)
+    crass (1.0.5)
     docile (1.3.2)
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
@@ -82,7 +82,7 @@ GEM
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
     json (2.2.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -100,7 +100,7 @@ GEM
     multi_json (1.13.1)
     netrc (0.11.0)
     nio4r (2.5.2)
-    nokogiri (1.10.4)
+    nokogiri (1.9.1)
       mini_portile2 (~> 2.4.0)
     rack (2.0.7)
     rack-test (1.1.0)