chore(deps): bump sprockets from 2.12.4 to 2.12.5 (#2665)

Bumps [sprockets](http://getsprockets.org/) from 2.12.4 to 2.12.5.

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

Gemfile.lock

@@ -225,7 +225,7 @@ GEM
       asset_sync (~> 1.0.0)
       middleman-core (>= 3.0.0)
     mini_portile2 (2.4.0)
-    multi_json (1.12.1)
+    multi_json (1.13.1)
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
     nokogiri (1.10.3-x86-mingw32)
@@ -246,7 +246,7 @@ GEM
       nokogiri (~> 1.5)
       trollop (~> 2.1)
     sass (3.4.24)
-    sprockets (2.12.4)
+    sprockets (2.12.5)
       hike (~> 1.2)
       multi_json (~> 1.0)
       rack (~> 1.0)