Bump loofah from 2.2.3 to 2.4.0

Bumps [loofah](https://github.com/flavorjones/loofah) from 2.2.3 to 2.4.0.
- [Release notes](https://github.com/flavorjones/loofah/releases)
- [Changelog](https://github.com/flavorjones/loofah/blob/master/CHANGELOG.md)
- [Commits](flavorjones/loofah@v2.2.3...v2.4.0)

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

Author: dependabot[bot]

Gemfile.lock

@@ -74,7 +74,7 @@ GEM
       execjs
     coffee-script-source (1.12.2)
     concurrent-ruby (1.1.5)
-    crass (1.0.4)
+    crass (1.0.6)
     devise (4.6.1)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
@@ -106,7 +106,7 @@ GEM
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
-    loofah (2.2.3)
+    loofah (2.4.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)