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>

Author: dependabot[bot]

Gemfile.lock

@@ -59,7 +59,7 @@ GEM
       ffi (~> 1.0, >= 1.0.11)
     cocoon (1.2.12)
     concurrent-ruby (1.1.5)
-    crass (1.0.4)
+    crass (1.0.5)
     cucumber (2.3.3)
       builder (>= 2.1.2)
       cucumber-core (~> 1.4.0)
@@ -122,7 +122,7 @@ GEM
     launchy (2.4.3)
       addressable (~> 2.3)
     libxml-ruby (3.1.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)