Bump mini_racer from 0.3.1 to 0.4.0

Bumps [mini_racer](https://github.com/discourse/mini_racer) from 0.3.1 to 0.4.0.
- [Release notes](https://github.com/discourse/mini_racer/releases)
- [Changelog](https://github.com/rubyjs/mini_racer/blob/master/CHANGELOG)
- [Commits](https://github.com/discourse/mini_racer/compare/v0.3.1...v0.4.0)

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

Gemfile

@@ -95,7 +95,7 @@ gem 'test-unit', '~> 3.4'
 gem 'coffee-rails', '~> 4.2.2'
 gem 'compass-rails'
 
-gem 'mini_racer', '0.3.1'
+gem 'mini_racer', '0.4.0'
 
 gem 'uglifier', '>= 1.0.3'
 

Gemfile.lock

@@ -311,7 +311,7 @@ GEM
       addressable (~> 2.3)
     letter_opener (1.7.0)
       launchy (~> 2.2)
-    libv8 (8.4.255.0)
+    libv8-node (15.14.0.0)
     loofah (2.9.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -323,8 +323,8 @@ GEM
     mime-types-data (3.2020.1104)
     mini_mime (1.0.3)
     mini_portile2 (2.5.0)
-    mini_racer (0.3.1)
-      libv8 (~> 8.4.255)
+    mini_racer (0.4.0)
+      libv8-node (~> 15.14.0.0)
     minitest (5.14.4)
     monetize (1.11.0)
       money (~> 6.12)
@@ -662,7 +662,7 @@ DEPENDENCIES
   kaminari (~> 1.2.1)
   knapsack
   letter_opener (>= 1.4.1)
-  mini_racer (= 0.3.1)
+  mini_racer (= 0.4.0)
   monetize (~> 1.11)
   oauth2 (~> 1.4.7)
   ofn-qz!