Bump sprockets from 3.7.1 to 3.7.2

Bumps [sprockets](http://getsprockets.org/) from 3.7.1 to 3.7.2.

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

Author: dependabot[bot]

Gemfile.lock

@@ -51,7 +51,7 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    concurrent-ruby (1.0.5)
+    concurrent-ruby (1.1.5)
     connection_pool (2.2.2)
     crass (1.0.4)
     debase (0.2.1)
@@ -89,7 +89,7 @@ GEM
       mini_portile2 (~> 2.3.0)
     public_suffix (3.0.2)
     puma (3.11.2)
-    rack (2.0.4)
+    rack (2.0.7)
     rack-proxy (0.6.4)
       rack
     rack-test (0.8.2)
@@ -165,7 +165,7 @@ GEM
     spring-watcher-listen (2.0.1)
       listen (>= 2.7, < 4.0)
       spring (>= 1.2, < 3.0)
-    sprockets (3.7.1)
+    sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)