Bump loofah from 2.2.3 to 2.3.1 (#2355)

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

@@ -55,14 +55,14 @@ GEM
     builder (3.2.3)
     byebug (11.0.1)
     concurrent-ruby (1.1.5)
-    crass (1.0.4)
+    crass (1.0.5)
     erubi (1.8.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
     jaro_winkler (1.5.2)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -75,7 +75,7 @@ GEM
     mini_portile2 (2.4.0)
     minitest (5.11.3)
     nio4r (2.3.1)
-    nokogiri (1.10.3)
+    nokogiri (1.9.1)
       mini_portile2 (~> 2.4.0)
     parallel (1.17.0)
     parser (2.6.3.0)