Updated gems, fix issues caused by the removal of $window from cyberarm_engine

Gemfile.lock

@@ -1,10 +1,10 @@
 GIT
   remote: https://github.com/cyberarm/cyberarm_engine
-  revision: 1b080f9fb99cc4ec696f32f00f28cbf89b40ed04
+  revision: ab9f9e8e7a4e02df7fefbb9b5add248b7629a2f7
   specs:
-    cyberarm_engine (0.18.0)
-      clipboard (~> 1.3.5)
-      excon (~> 0.78.0)
+    cyberarm_engine (0.21.0)
+      clipboard (~> 1.3)
+      excon (~> 0.88)
       gosu (~> 1.1)
       gosu_more_drawables (~> 0.3)
 
@@ -21,25 +21,23 @@ GIT
 GEM
   remote: https://rubygems.org/
   specs:
-    clipboard (1.3.5)
-    concurrent-ruby (1.1.8)
+    clipboard (1.3.6)
+    concurrent-ruby (1.1.10)
     cri (2.1.0)
-    excon (0.78.1)
-    gosu (1.2.0)
+    excon (0.92.3)
+    gosu (1.4.3)
     gosu_more_drawables (0.3.1)
-    i18n (1.8.10)
+    i18n (1.11.0)
       concurrent-ruby (~> 1.0)
     mini_portile2 (2.8.0)
     nokogiri (1.13.6)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
-    nokogiri (1.13.6-x64-mingw32)
-      racc (~> 1.4)
     ocra (1.3.11)
-    opengl-bindings (1.6.11)
+    opengl-bindings (1.6.12)
     racc (1.6.0)
-    rake (13.0.3)
-    rubyzip (2.3.0)
+    rake (13.0.6)
+    rubyzip (2.3.2)
 
 PLATFORMS
   ruby
@@ -57,4 +55,4 @@ DEPENDENCIES
   rubyzip
 
 BUNDLED WITH
-   2.2.3
+   2.3.17