Bump sprockets from 2.12.4 to 2.12.5

Bumps [sprockets](https://github.com/rails/sprockets) from 2.12.4 to 2.12.5.
- [Release notes](https://github.com/rails/sprockets/releases)
- [Changelog](https://github.com/rails/sprockets/blob/master/CHANGELOG.md)
- [Commits](rails/sprockets@v2.12.4...v2.12.5)

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

Gemfile.lock

@@ -92,7 +92,7 @@ GEM
       rouge (~> 1.0)
     mini_portile2 (2.4.0)
     minitest (5.8.4)
-    multi_json (1.11.2)
+    multi_json (1.14.1)
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     padrino-helpers (0.12.5)
@@ -112,7 +112,7 @@ GEM
     redcarpet (3.3.4)
     rouge (1.10.1)
     sass (3.4.21)
-    sprockets (2.12.4)
+    sprockets (2.12.5)
       hike (~> 1.2)
       multi_json (~> 1.0)
       rack (~> 1.0)