Bump libv8 in appraisal gemfiles from v7.3 to v8.4

This fixes a copmilation error on TravisCI.

Author: ksylvest

gemfiles/rails_5.2_no_sprockets.gemfile.lock

@@ -130,7 +130,7 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.13.0)
+    minitest (5.14.2)
     nenv (0.3.0)
     nio4r (2.5.2)
     nokogiri (1.10.7)
@@ -232,4 +232,4 @@ DEPENDENCIES
   webdrivers
 
 BUNDLED WITH
-   2.1.2
+   2.2.3

gemfiles/rails_5.2_no_sprockets_webpacker_3.gemfile.lock

@@ -115,7 +115,7 @@ GEM
     jbuilder (2.9.1)
       activesupport (>= 4.2.0)
     json (2.3.0)
-    libv8 (7.3.492.27.1-x86_64-darwin-18)
+    libv8 (8.4.255.0)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -131,9 +131,9 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    mini_racer (0.2.8)
-      libv8 (>= 6.9.411)
-    minitest (5.13.0)
+    mini_racer (0.3.1)
+      libv8 (~> 8.4.255)
+    minitest (5.14.2)
     nenv (0.3.0)
     nio4r (2.5.2)
     nokogiri (1.10.7)
@@ -244,4 +244,4 @@ DEPENDENCIES
   webpacker (~> 3.0)
 
 BUNDLED WITH
-   2.1.2
+   2.2.3

gemfiles/rails_5.2_no_sprockets_webpacker_4.gemfile.lock

@@ -115,7 +115,7 @@ GEM
     jbuilder (2.9.1)
       activesupport (>= 4.2.0)
     json (2.3.0)
-    libv8 (7.3.492.27.1-x86_64-darwin-18)
+    libv8 (8.4.255.0)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -131,9 +131,9 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    mini_racer (0.2.8)
-      libv8 (>= 6.9.411)
-    minitest (5.13.0)
+    mini_racer (0.3.1)
+      libv8 (~> 8.4.255)
+    minitest (5.14.2)
     nenv (0.3.0)
     nio4r (2.5.2)
     nokogiri (1.10.7)
@@ -244,4 +244,4 @@ DEPENDENCIES
   webpacker (~> 4.0)
 
 BUNDLED WITH
-   2.1.2
+   2.2.3

gemfiles/rails_5.2_sprockets_3.gemfile.lock

@@ -115,7 +115,7 @@ GEM
     jbuilder (2.9.1)
       activesupport (>= 4.2.0)
     json (2.3.0)
-    libv8 (7.3.492.27.1)
+    libv8 (8.4.255.0)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -131,9 +131,9 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    mini_racer (0.2.8)
-      libv8 (>= 6.9.411)
-    minitest (5.13.0)
+    mini_racer (0.3.1)
+      libv8 (~> 8.4.255)
+    minitest (5.14.2)
     nenv (0.3.0)
     nio4r (2.5.2)
     nokogiri (1.10.7)
@@ -242,4 +242,4 @@ DEPENDENCIES
   webdrivers
 
 BUNDLED WITH
-   2.1.2
+   2.2.3

gemfiles/rails_5.2_sprockets_4.gemfile.lock

@@ -115,7 +115,7 @@ GEM
     jbuilder (2.9.1)
       activesupport (>= 4.2.0)
     json (2.3.0)
-    libv8 (7.3.492.27.1-x86_64-darwin-18)
+    libv8 (8.4.255.0)
     listen (3.0.8)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -131,9 +131,9 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    mini_racer (0.2.8)
-      libv8 (>= 6.9.411)
-    minitest (5.13.0)
+    mini_racer (0.3.1)
+      libv8 (~> 8.4.255)
+    minitest (5.14.2)
     nenv (0.3.0)
     nio4r (2.5.2)
     nokogiri (1.10.7)
@@ -242,4 +242,4 @@ DEPENDENCIES
   webdrivers
 
 BUNDLED WITH
-   2.1.2
+   2.2.3