DEV: Use the release version of sprockets (#26490)

Gemfile

@@ -19,7 +19,7 @@ gem "json"
 
 # TODO: At the moment Discourse does not work with Sprockets 4, we would need to correct internals
 # We intend to drop sprockets rather than upgrade to 4.x
-gem "sprockets", git: "https://github.com/rails/sprockets", branch: "3.x"
+gem "sprockets", "~> 3.7.3"
 
 # this will eventually be added to rails,
 # allows us to precompile all our templates in the unicorn master

Gemfile.lock

@@ -1,13 +1,3 @@
-GIT
-  remote: https://github.com/rails/sprockets
-  revision: 0487291ad2527d1303f2692a558c21f38a6169f1
-  branch: 3.x
-  specs:
-    sprockets (3.7.3)
-      base64
-      concurrent-ruby (~> 1.0)
-      rack (> 1, < 3)
-
 GEM
   remote: https://rubygems.org/
   specs:
@@ -483,6 +473,10 @@ GEM
     snaky_hash (2.0.1)
       hashie
       version_gem (~> 1.1, >= 1.1.1)
+    sprockets (3.7.3)
+      base64
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
     sprockets-rails (3.4.2)
       actionpack (>= 5.2)
       activesupport (>= 5.2)
@@ -660,7 +654,7 @@ DEPENDENCIES
   shoulda-matchers
   sidekiq
   simplecov
-  sprockets!
+  sprockets (~> 3.7.3)
   sprockets-rails
   sqlite3
   sshkey