Merge pull request #216 from ohbarye/dependabot/bundler/backend/loofah-2.3.1

[Security] Bump loofah from 2.2.3 to 2.3.1 in /backend

Author: ohbarye

backend/Gemfile.lock

@@ -74,7 +74,7 @@ GEM
     childprocess (2.0.0)
       rake (< 13.0)
     concurrent-ruby (1.1.5)
-    crass (1.0.4)
+    crass (1.0.5)
     erubi (1.8.0)
     ffi (1.10.0)
     globalid (0.4.2)
@@ -87,7 +87,7 @@ GEM
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)