Bump sprockets from 3.7.1 to 4.0.0 in /spec/jsonapi_app

Bumps [sprockets](https://github.com/rails/sprockets) from 3.7.1 to 4.0.0.
- [Release notes](https://github.com/rails/sprockets/releases)
- [Changelog](https://github.com/rails/sprockets/blob/master/CHANGELOG.md)
- [Commits](rails/sprockets@v3.7.1...v4.0.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

spec/jsonapi_app/Gemfile.lock

@@ -40,7 +40,7 @@ GEM
       tzinfo (~> 1.1)
     arel (7.1.4)
     builder (3.2.3)
-    concurrent-ruby (1.0.5)
+    concurrent-ruby (1.1.5)
     crass (1.0.5)
     database_cleaner (1.6.1)
     erubis (2.7.0)
@@ -71,7 +71,7 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (0.21.0)
     puma (3.9.1)
-    rack (2.0.3)
+    rack (2.0.7)
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (5.0.5)
@@ -101,7 +101,7 @@ GEM
     rb-fsevent (0.10.2)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    sprockets (3.7.1)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.0)