Bump ruby to 2.6.6 and speed up docker build

Gemfile.lock

@@ -135,7 +135,7 @@ GEM
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
-    loofah (2.15.0)
+    loofah (2.16.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -144,17 +144,15 @@ GEM
     matrix (0.4.2)
     method_source (1.0.0)
     mini_mime (1.1.2)
-    mini_portile2 (2.8.0)
     minitest (5.15.0)
     momentjs-rails (2.29.1.1)
       railties (>= 3.1)
-    msgpack (1.4.5)
+    msgpack (1.5.1)
     nio4r (2.5.8)
-    nokogiri (1.13.3)
-      mini_portile2 (~> 2.8.0)
+    nokogiri (1.13.3-x86_64-linux)
       racc (~> 1.4)
     orm_adapter (0.5.0)
-    pg (1.3.4)
+    pg (1.3.5)
     public_suffix (4.0.6)
     puma (4.3.12)
       nio4r (~> 2.0)
@@ -194,7 +192,7 @@ GEM
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    react-rails (2.6.1)
+    react-rails (2.6.2)
       babel-transpiler (>= 0.7.0)
       connection_pool
       execjs
@@ -235,7 +233,7 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
-    sassc (2.4.0)
+    sassc (2.1.0-x86_64-linux)
       ffi (~> 1.9)
     sassc-rails (2.1.2)
       railties (>= 4.0.0)
@@ -308,6 +306,7 @@ DEPENDENCIES
   react-rails (~> 2.6.0)
   rspec-rails (~> 3.8.2)
   sass-rails (~> 5)
+  sassc (= 2.1.0)
   selenium-webdriver
   spring
   spring-watcher-listen (~> 2.0.0)
@@ -318,7 +317,7 @@ DEPENDENCIES
   webpacker (~> 4.0)
 
 RUBY VERSION
-   ruby 2.6.3p62
+   ruby 2.6.6p146
 
 BUNDLED WITH
    1.17.2