Update dependency sprockets to v4

Author: renovate[bot]

api/Gemfile

@@ -72,7 +72,7 @@ group :development do
   gem 'listen', '~> 3.3'
   # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
-  gem 'sprockets', '~> 3.7.2'
+  gem 'sprockets', '~> 4.2.0'
   gem 'graphiql-rails'
 end
 

api/Gemfile.lock

@@ -78,7 +78,7 @@ GEM
     code_analyzer (0.5.5)
       sexp_processor
     colorize (1.1.0)
-    concurrent-ruby (1.2.2)
+    concurrent-ruby (1.2.3)
     crass (1.0.6)
     database_cleaner-active_record (2.1.0)
       activerecord (>= 5.a)
@@ -305,9 +305,9 @@ GEM
     spring (4.1.1)
     spring-commands-rspec (1.0.4)
       spring (>= 0.9.1)
-    sprockets (3.7.2)
+    sprockets (4.2.1)
       concurrent-ruby (~> 1.0)
-      rack (> 1, < 3)
+      rack (>= 2.2.4, < 4)
     sprockets-rails (3.4.2)
       actionpack (>= 5.2)
       activesupport (>= 5.2)
@@ -372,7 +372,7 @@ DEPENDENCIES
   slack-notifier
   spring
   spring-commands-rspec
-  sprockets (~> 3.7.2)
+  sprockets (~> 4.2.0)
   tzinfo-data
 
 RUBY VERSION